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A Primer on the NBA’s Plus-Minus Statistics

Ben Dowsett explains what plus-minus is and how it can be used to better understand each NBA player’s impact.

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Modern basketball analysis contains a plethora of advanced statistics and metrics to help us better understand and parse what’s going on out there on the floor. We can go beyond simple measures like points, rebounds and assists to contextualize the game more effectively – from metrics like true shooting percentage that help track the value of shots to advances like SportVU data that help us dig into the granular level of every pass, shot and rebound.

Growing in popularity within the analytics community over the last several years has been another metric: Plus-minus. The term sounds simple enough, but what exactly is it? Let’s break it down in simple terms even the casual fan can understand.

What is Plus-Minus?

In its simplest form, plus-minus is exactly what it sounds like – when a given player is on the floor, be it for a single game, group of games or a season, does his team get outscored or does it outscore the opponent? This very simple metric is housed in most common single-game box scores, and is the rawest way of determining what sort of effect a player has on his team (and the opponent) while on the court.

The results of such a simple statistic can often have tons of noise involved, however, and those in the statistical community have derived more advanced measures to help add detail and context. This process, and the resulting outputs, are most commonly referred to as Adjusted Plus-Minus (APM).

There are a number of different well-known types of APM metrics, each of which uses slightly different techniques to reach their final output. The most basic goal is to account for the other players on the floor when establishing a guy’s total, and this can be done by adjusting a number of different variables. The statistician can control for such elements as coaching, opponent, time in between games and more. They can also use longer stretches of prior games to “inform” the model (the process of setting a concrete statistical baseline with which to compare subsequent players). There are also formats known as Statistical Plus-Minus, which include elements of standard box scores as well.

What Can We Learn From Plus-Minus?

The answer here will vary somewhat depending on which version we’re viewing, but the general goal remains to contextualize the effect a player has on his team and opponents while accounting for as many situations and player combinations as possible. Rather than tracking what a player accomplishes individually, the idea is to determine what each individual player’s cumulative contribution has meant to what their team does while they’re on the floor.

Beyond this, the details will depend on the model. ESPN’s Real Plus-Minus, for instance, factors in both teammate and opponent context for each individual player, and also has an element of box score statistics involved – it’s among the more complex measures out there, and generally considered one of the more “accurate,” so far as such a term confirms what we already can glean about players.

Let’s look at a simple example of how this sort of thing can be useful even for the casual observer:

Quantifying a player’s defensive abilities has always been one of the toughest areas within analytics. Anyone with a keen eye and experience can get a good rough idea by watching players, and one can use NBA.com’s advanced on/off court logs to determine that a team tends to suffer defensively when one particular player steps on or off the court. There are a few other tracking services (such as Synergy Sports and SportVU cameras) that can assist us here.

These are helpful things to know, but they’re limited. What if, for instance, a guy has bad on/off numbers which would indicate that he’s a defensive liability, but in reality he simply plays a huge portion of his minutes with at least one other bad defensive player? That’s where APM metrics come in. By aggregating figures neither our brains nor simple on/off measures could ever keep track of over long periods of time, they can do a much better job of separating the true causes of a team’s positive or negative play on an individual level.

Now, none of these metrics are perfect by any means – it’s why there are so many variations favoring slightly different approaches. No stat can track how well a guy contests a shot, or whether he pushes himself to 100 percent to get around every single screen set against him. But because these metrics touch so many individual data points that help smooth out incongruities, the guys who make these sorts of “non-trackable” plays will almost always eventually show through in APM outputs.

Who Are Some Plus-Minus Outliers?

Part of what helps indicate the effectiveness of a metric like Real Plus-Minus is the fact that a look at the top of the rankings typically reveals all the guys we’d think of as the best players in the league. Last season’s top five for RPM, in order, were: Stephen Curry, LeBron James, James Harden, Anthony Davis and Kawhi Leonard – or in other words, the top three MVP vote-getters, the Defensive Player of the Year, and the best under-22 player since LeBron at that age.

That said, each iteration of APM will highlight several outliers on both ends of the spectrum: guys who the models either like or dislike in stark contrast with what consensus opinions of them tend to be.

Last year’s prime example here would be Milwaukee’s Khris Middleton, who finished 10th overall for RPM despite coming into the year as a relatively unknown player. A large factor was the way his impact on the court for the Bucks was consistently felt even when he wasn’t putting up traditional numbers.

His versatility defensively is a huge plus – Middleton’s capability to guard up to four positions in the right situations made him a plug-and-play piece who could fit with plenty of different lineup combinations. In the long run, these elements plus Middleton’s ability to stay within his role on both ends of the floor made him a Plus-Minus All-Star, and there’s no question the rise in prevalence of these measures at the front office level contributed to him receiving a hefty pay day last offseason.

There are several others as well – Kyle Korver has always rated very well, and guys like Draymond Green and Tony Allen can look to APM metrics as some of the greatest representations of their value on the floor. Michael Kidd-Gilchrist is another who sees his defensive contributions accurately reflected even when traditional stats are unable to do so. In general, while we do see examples of big positive outliers offensively, the majority of them tend to come on the defensive end where aggregating counting stats has always been more difficult.

On the other side of the coin, traditional stats have inflated certain players’ reputations to a point that APM metrics disagree with, sometimes strongly. Enes Kanter is one example – he was 45th of 55 centers for total RPM last season, and was dead last among these same 55 for isolated Defensive RPM. And yet, Kanter still managed to ink a gigantic deal in restricted free agency. Carmelo Anthony is another, finishing just 400th of 474 total players last season mainly due to a big negative figure defensively – confirming to many the prevalent opinion that he’s a one-way player and short of a true superstar for that reason.

A word of caution, one that could be applied to any single-number metric out there: This is not an end-all statistic. A simple look at RPM rankings, or those of any other APM derivative, is not a surefire way of determining which players are “better” than others in any sort of concrete sense. These metrics have error margins, and even their creators would acknowledge that there will always be parts of the game they struggle to pick up entirely. They also don’t do a good job at all of telling us why certain guys rate so highly, a determination that can be tough at times.

Still, APM and plus-minus in general have a number of very effective uses. The ability to contextualize the effect a guy is having on his team over the long run, with a keen eye to certain situations or combinations that may be leaning heavily on his overall production, is a valuable one. Plus-minus metrics aren’t going anywhere, and will only become more useful as our best statisticians figure out ways to make them even more reliable and less prone to error.

Ben Dowsett is a Deputy Editor and in-depth basketball analyst based in Salt Lake City. He covers the Jazz on a credentialed basis for Basketball Insiders, and has previously appeared in the Sports Illustrated and TrueHoop Networks. He can be found on Twitter at @Ben_Dowsett.

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NBA Daily: Wiggins The X-Factor for Warriors

Stephen Curry will always be the face of the Golden State Warriors, and for good reason. Draymond Green spearheads their defensive attack but the key to their postseason fate lies in the hands of a guy that many people had already given up on.

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The 2020-21 regular season was a strange one for many reasons, but especially for the Golden State Warriors. Shortly before the NBA Draft, the team’s championship aspirations took a major hit with the injury to Klay Thompson. The best backcourt in the league would not be on full display this season, but they still had two-time MVP, Stephen Curry, to put on a show.

Curry did just that, dazzling basketball fans on a near-nightly basis. The sensational shots, ridiculous plays and high-drama situations were must-see TV that kept the Warriors in the national spotlight. To that end, Curry captured the scoring title for the second time in his career, averaging 32.0 points per game this season.

With limited options available to fill Thompson’s void, the team managed to add Kelly Oubre Jr to the roster, although it came at a steep cost. His salary is $14.4 million this season but because of Golden State’s luxury tax bill, ESPN’s Bobby Marks noted that adding Oubre would cost an additional $82.4 million, bringing their total to $134 million.

After a career year in Phoenix, Oubre struggled mightily trying to fit in with this group. Sometimes players in new situations can try to do too much at first, or sometimes pass on open shots in order to not seem selfish. Neither of these was the case for Oubre, who simply could not put the ball in the basket. His early-season shooting struggles had the Warriors pegged for the Draft Lottery.

Oubre eventually turned it around and began playing like himself. Another new face in the Bay area was rookie James Wiseman. He too struggled at the beginning of the season, which is to be expected for someone in his situation. The seven-footer from Memphis only played a handful of games in college and was trying to learn the NBA game on the fly. A season-ending injury cut short his rookie season, but he showed promise for the future.

The future is not something that Curry has on his mind. He and Draymond Green are playing to win now. That starts on Wednesday with their highly-anticipated showdown with LeBron James, Anthony Davis and the defending NBA champion Los Angeles Lakers. The league has quite the matchup to cap the new Play-In-Tournament.

Amid all of the highlight plays from Curry and all of the noise surrounding Green, one player sits in the shadows and is rarely mentioned. Andrew Wiggins was all the rage when he was selected number one overall in the 2014 NBA Draft. The former Kansas Jayhawk earned Rookie of the Year honors but ultimately struggled to find his place in Minneapolis.

After more than five seasons with the Minnesota Timberwolves, Wiggins was traded to the Warriors in February of last season. Now having played a full season in a Warriors uniform, Wiggins could be their x-factor in the postseason.

One of the knocks on Wiggins has always been his drive, and his passion to reach his full potential. He has all of the physical tools and attributes to be one of the most prolific two-way players in the league. Sometimes the effort just isn’t there, but that narrative seems to have gone out the window. Wiggins has been playing excellent on both ends of the floor, which has translated to wins for the depleted Warriors.

While many people point to his scoring slightly declining, he still scored 19 points per game despite playing the fewest minutes of his career. He finished inside the top 40 in scoring this season. The real story for Wiggins is his efficiency, which has been incredible. He shot a career-high 48 percent from the floor this season and a career-best 38 percent from three-point range. His 54 percent effective field goal percentage is also the highest of his career.

As they prepare to battle the Lakers for the 7th seed in the Western Conference, Golden State must find ways to get stops on the defensive end. Stopping the likes of James, Davis and Dennis Schroder on the perimeter will be paramount to their success. It is easier said than done, but this is where Wiggins’ value can be felt. The Toronto native will be called upon to match up against James often, with Green defending their big men.

Wiggins finished fourth in Defensive RPM (2.72) this season at his position, 21st among all players in the league. That is by far the best of his career, as he ranked 85th last season among small forwards. He also finished inside the top five in the league in terms of contested three-point shots. That is important for the Warriors going forward, should they face the Phoenix Suns or Utah Jazz in the first round. Utah was the top three-point shooting team in the league and Phoenix was seventh-best in terms of percentage.

As if facing James and Davis weren’t difficult enough, the Warriors will have their hands full no matter which opponent they face next. Both have dynamic backcourts with Mike Conley/Donovan Mitchell in Utah and Chris Paul/Devin Booker in Phoenix. Wiggins will be tasked with trying to slow them down as well. There is elite talent everywhere you look out West.

Golden State finished the regular season with a 110.1 defensive rating, which was top five in the league. They managed to do that despite having a depleted roster and having the third-highest pace (102.2) in the league. Much of the credit will go to Green and Oubre but Wiggins has been a major factor in their defensive schemes.

Curry and Green have combined to play in 235 playoff games during their careers. Wiggins has only appeared in five playoff games, so this will be a new experience for him. The pressure always goes up in the postseason, and the Play-In Tournament is no exception.

Shortly after acquiring Wiggins, Steve Kerr put All-Defense expectations on him. “Defensively, we will ask him to take on the challenge of what that position entails. Guarding some of the best players in the league and adapting to our schemes and terminology.” To his credit, Wiggins has done just that.

Wiggins will not win the NBA’s Most Improved Player Award this season. He isn’t going to win the Defensive Player of the Year either. While those accolades matter to a lot of players, Wiggins is just focused on improving and winning games. The Warriors hope to do the same as they return to postseason play.

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NBA Daily: Examining Michael Porter Jr.’s Ascension

Since Jamal Murray’s season-ending knee injury, Michael Porter Jr. is averaging over 25 points per game and looks like a future All-NBA player. Bobby Krivitsky examines Porter’s ascent and the questions that come with it.

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Since Jamal Murray’s season-ending knee injury, Michael Porter Jr. has taken his game to new heights.

In the wake of Murray’s ACL tear in mid-April, Porter’s playing time has gone from 30.6 minutes per contest to 35.7, while his shots per game have risen from 12.6 per game to 16.5. The increased responsibility has fueled his ascent. He’s knocking down 56.3 percent of those attempts. He’s taking 8.2 threes per game and making a blistering 50 percent of them. As a result, Porter’s gone from averaging 17.5 points per game to 25.1. He’s also grabbing 6.1 rebounds and blocking almost one shot per contest.

At the time of Murray’s injury, the Denver Nuggets were in fourth place in the Western Conference. They remain there now, 9-4 in his absence, and they boast the eighth-highest net rating in the NBA.

The only way for the Nuggets to fall from fourth would be if they lost their four remaining games and the Dallas Mavericks won their final five contests because the Mavericks have the tiebreaker since they won the season series. On the more realistic end of the spectrum, Denver sits just 1.5 games back of the Los Angeles Clippers, who occupy the third seed in the West. The Nuggets won their season series against the Clippers, meaning they’d finish in third if the two teams ended the regular season with the same record.

There’s a bevy of questions surrounding Porter’s recent play that need to be asked but cannot get answered at the moment. That starts with whether this is anything more than a hot streak. While it’s impossible to say definitively, it’s reasonable to believe Porter can consistently and efficiently produce about 25 points per game. He was the second-ranked high school prospect in 2017 and entered his freshman year at Missouri firmly in the mix for the top pick in the 2018 NBA draft. That was thanks in large part to his offensive prowess as a 6-10 wing with a smooth shot that’s nearly impossible to block because of the elevation he gets when he shoots. 

A back injury cost him all but 53 minutes of his collegiate career and caused him to fall to the 14th pick in the draft. He ended up in an ideal landing spot, going to a well-run organization that’s also well aware of its barren track record luring star players looking to change teams, making it vital for the Nuggets to hit on their draft picks. 

Porter’s first year in the NBA was exclusively dedicated to the rehab process and doing everything possible to ensure he can have a long, healthy and productive career. Last season, finally getting a chance to play, he showed off the tantalizing talent that made him a top prospect but only took seven shots per game while trying to fit in alongside Nikola Jokic, Murray, Paul Millsap and Jerami Grant.

More experience, including battling against the Los Angeles Lakers in the Western Conference Finals, an offseason, albeit a truncated one, to prepare for a more substantial role with Grant joining the Detroit Pistons and Millsap turning 36 this year, helped propel Porter. 

But for the Nuggets, before Murray’s injury, the perception was that even though they weren’t the favorites to come out of the Western Conference, they were a legitimate title contender. How far can they go if Porter’s consistently contributing about 25 points and over six rebounds per game while effectively playing the role of a second star alongside Jokic? 

It seems fair to cross Denver off the list of title contenders. But, if Porter continues to capably play the role of a second star alongside Jokic when doing so becomes more challenging in the postseason, the Nuggets can advance past a team like the Mavericks or Portland Trail Blazers. And at a minimum, they’d have the ability to make life difficult for whoever they had to face in the second round of the playoffs.

Unfortunately, the timing of Murray’s ACL tear, which happened in mid-April, means there’s a legitimate possibility he misses all of next season. Denver’s increased reliance on Porter is already allowing a young player with All-NBA potential to take on a role that’s closer to the one he’s assumed his whole life before making it to the sport’s highest level. If the Nuggets are counting on him to be the second-best player on a highly competitive team in the Western Conference next season, it’ll be fascinating to see what heights he reaches and how far they’re able to go as a team.

Theoretically, Porter’s growth could make it difficult for Denver to reacclimate Murray. But given Jokic’s unselfish style of play, there’s room for both of them to be satisfied by the volume of shots they’re getting. Unfortunately, the Nuggets have to wait, potentially another season, but Jokic is 26-years-old, Murray 24, Porter 22. When Denver has their Big Three back together, they could be far more potent while still being able to enjoy a lengthy run as legitimate title contenders.

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NBA Daily: D’Angelo Russell Back on Track

D’Angelo Russell lost much of the 2020-21 season to injury. Drew Maresca explains why his return will surprise people around the league.

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D’Angelo Russell was traded to the Minnesota Timberwolves last February, just before the COVID-19 pandemic shut down the entire season. But we’ve yet to see what Russell can really do in Minnesota.

The Timberwolves acquired Russell in late February in exchange for a future first-round pick – which transitions this season if they pick later than third – a 2021 second-round pick and Andrew Wiggins.

Sidenote: For those keeping score at home, the Timberwolves currently have the third-worst record in the league with five games remaining. It would behoove Minnesota to lose as many of their remaining games as possible to keep their 2021 pick. If the pick does not transition this season, it becomes unrestricted in 2020.

Trying to turn an owed pick into an unprotected future first is usually the wrong move; but in this instance, it’s better to keep the high first-rounder this year with an understanding that your 2022 pick will probably fall in or around the middle of the lottery.

The thinking around the deal was that Minnesota could qualify for the playoffs as soon as this season by swapping Wiggins’ contract for a young, talented lead guard in Russell. It has not played out as planned.

COVID resulted in a play stoppage shortly after the deal, robbing Russell of the opportunity to ramp up with his new team. When the NBA returned to finish the 2019-20 season, the Timberwolves failed to qualify for bubble play – and considering the US was still battling a global pandemic, Russell couldn’t easily practice with his new teammates and/or coaches.

The 2020-21 season began weirdly, too. The NBA proceeded with an abbreviated training camp and preseason. And while this impacted all teams, Russell was additionally hindered by the decision.

Ready or not, the season began. In 2020-21, Russell is averaging a near-career low in minutes per game (28.2) across just 36 games. He’s tallying 19.1 points per game on 43.6% shooting and a career-best 38.8% on three-point attempts. He’s also he’s posting a near career-best assist-to-turnover ratio (5.7 to 2.8).

Despite Russell’s contributions, the Timberwolves have failed to meet expectations. Far from the playoff squad they hoped to be, Minnesota is in contention for the top pick in this year’s draft. So what has gone wrong in Minneapolis?

Russell’s setbacks are fairly obvious. In addition to the lack of preparation with his teammates and coaches, Russell was diagnosed with a “loose body” in his knee, requiring arthroscopic knee surgery in February. As a result, he missed 27 consecutive games. Russell returned on April 5, but head coach Chris Finch revealed that he’d been on a minutes restriction until just recently.

Minnesota is clearly being cautious with Russell. Upon closer review, Russell has been restricted to under 30 minutes per game in all of his first 10 games back. Since then, Russell is averaging 31 minutes per game including an encouraging 37 minutes on May 5 in a four-point loss to Memphis.

Since returning from knee surgery, Russell is averaging 27 minutes per game across 16 games. Despite starting 19 of the team’s first 20 games, he hadn’t started in any game since returning – until Wednesday.

On the whole, Russell’s impact is about the same as it was prior to the injury, which should be encouraging to Timberwolves’ fans. He’s scoring slightly less (18.8 points since returning vs. 19.3 prior), shooting better from the field (44.9% since returning vs 42.6%% prior) and has been just slightly worse from three-point range (37.4% since vs. 39.9 prior). He’s dishing out more assists per game (6.5 since vs. 5.1 prior), too, and he posted three double-digit assist games in his last five contents – a feat achieved only once all season prior to his last five games.

Despite playing more and dropping more dimes, there’s still room to improve. Looking back to his career-bests, Russell averaged 23.1 points per game in 2019-20 in 33 games with Golden State (23.6) and 12 games with Minnesota (21.7).

But his most impactful season came in 2018-19 with the Brooklyn Nets. That season, Russell averaged 21.1 points and 7.0 assists per game, leading the Nets to the playoffs and earning his first trip to the All-Star game. He looked incredibly comfortable, playing with supreme confidence and flashing the ability to lead a playoff team.

At his best, Russell is a dynamic playmaker. The beauty of Russell is that he can also play off the ball. He has a quick release on his jumper and impressive range. His game is not predicated on athleticism, meaning he should stay at his peak for longer than guys like De’Aaron Fox and Ja Morant.

And while he’s been in the league for what feels like ever (six seasons), Russell just turned 25 approximately two months ago. Granted, comparing anyone to Steph Curry is unwise, but Curry wasn’t Steph Curry yet at 25. Former MVP Steve Nash hadn’t yet averaged double-digits (points) at 25. Twenty-five is also an inflection point for Damian Lillard and Russell Westbrook. And the list goes on.

To be fair, Russell was drafted at 19 so he’s more acclimated to the league at this age than most, but his game will continue expanding nonetheless. He’ll develop trickier moves, become stronger and grow his shooting range. And a good deal of that growth should be evident as soon as next season since he’ll be fully healed from knee surgery and have a full offseason and training camp to finally work with teammates and coaches.

So while Minnesota’s 2020-21 season was incredibly bleak, their future is quite bright – and much of it has to do with the presence of Russell.

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