What better way to find a player’s value than examining whether the team wins or loses when they’re on the court? That’s the power of plus-minus.

During a nation­al­ly-tele­vised NBA game, ABC’s cam­eras picked up a con­ver­sa­tion between Golden State Warriors coach Steve Kerr and star shoot­er Stephen Curry, who was in the midst of a poor shoot­ing night.

“That’s your shoot­ing totals. That’s your plus-minus,” Kerr said, while show­ing Curry a stats sheet. ​“Alright? So it’s not always tied togeth­er. You’re doing great stuff out there. The tem­po is so dif­fer­ent when you’re out there. Everything you gen­er­ate for us is so pos­i­tive. It always shows up here [points to plus-minus]. You’re doing great. Carry on, my son.”

Plus-minus has become a favored stat among basketball coach­es because it shows how the team per­formed when a cer­tain play­er is on the floor. It goes beyond points, rebounds and oth­er tra­di­tion­al stats to paint­ a more com­plete pic­ture of one player’s impact at both ends of the court.

“When it comes down to it, num­bers don’t lie,” Ryan Fretz, the head coach of Clyde High School (Ohio), said. ​“We’re up front about it. We’ll show [the play­ers] the num­bers. If you want more play­ing time, you’ve got to progress here. It gets us look­ing at the num­bers out­side of points, rebounds and assists.”

How It Works

Plus-minus qualifies how you’re performing across all 85 feet of the floor—not just the 22 feet around your opponent’s basket. Let’s take a look at the box score from a recent boys basketball state playoff game. Team A below lost by a dozen, despite a respectable 16-point effort from Andrew Abraham in 26 minutes.

Contrast that with Team B here, which is full of plus-minus totals in the double-digits.

Jake States led the team in this stat despite a paltry 2-for-7 night from the floor. How? Because he filled up the stat sheet in other ways in fewer minutes than the team’s leading scorer.  

Let’s take a look at it from an NBA viewpoint. Two-time Defensive Player of the Year Rudy Gobert is never going to be mistaken for an offensive dynamo, but his plus-minus fig­ure from a recent season actually fared better than perennial MVP candidate James Harden.

Gobert’s box score stats don’t give him the appear­ance of a game-chang­er, but fac­tor­ing in his defense shows his true value

A play­er can score 20 points in a game, but if they’re sim­ply hunt­ing shots, not involv­ing oth­ers and play­ing shod­dy defense, are they really help­ing the team?

Plus-minus isn’t a fool­proof way to gauge defense, but can shine a light on some less-her­ald­ed players.

How Coaches Value It

As coaches tinker with their substitution patterns and how they stagger minutes for their star players, they’re using plus-minus to help separate the rubber from the road. 

It’s often particularly resourceful when it comes to evaluating role players off the bench, and what kind of energy they bring to the floor.

“They’re not perfect stats for us, but when you have a bench girl come in and she’s plus-four in five minutes, you go, okay, she’s obviously helping out,” says Lynden Christian (Wash.) girls basketball coach Brady Bomber. “That’s one of our favorite conversations. ‘Okay, this girl was plus-7, why is that? Is it because she’s playing with all the better starters so she’ll get better minutes?’ 

“But it’s nice for us because we win some games by a lot and others are more competitive, and we can filter out the games that weren’t competitive and just look at those stats for the competitive games.”

It goes the other way, too. Plus-minus data from scout film helps coaches make deeper discoveries. If your opponent is paying attention, that plus-four girl off the bench might be getting more minutes. What are her tendencies? How does she move without the ball? What should you take away from her when she’s on the floor?

How You Can Use It

One of the best ways to use plus-minus is in deter­min­ing which play­ers should be on the floor togeth­er. By look­ing through the line­up data, you can see which com­bi­na­tions played well togeth­er and outscored the opponent.

The plus-minus of line­up data high­lights who meshes well. It’s a sim­ple way to help you find your strongest combinations. But like any stat, it isn’t totally flaw­less. 

You should take into account when a play­er was on the floor (an ath­lete play­ing against all reserves might not play as well against the oppos­ing starters) and sam­ple size.

But when com­bined with oth­er rel­e­vant sta­tis­tics like VPS and the Four Factors, it helps uncov­er impor­tant infor­ma­tion that may otherwise slip through the cracks. After all, it’s lit­er­al­ly a mea­sure of win­ning and los­ing. What’s more valuable than that?

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