Player tracking transforming NBA analytics

The Mavericks were analyzing motion sensor data in their 2010-11 championship season. Glenn James/NBAE/Getty Images

You ever wonder what NBA assistant coaches are scribbling on their clipboards during games?

They’re taking down stats. But not the stats you’ll read in any box score. They’re logging numbers like touches in the paint, passes per possession, three-pointers off kick-out passes, secondary assists, fouls drawn –- information central to a game’s outcome but not found anywhere near a traditional box score.

This is how it’s been for years.

But the stats being tracked by these blazer-wearing NBA lifers -- both during the game and in the film room -- are nothing compared to what’s being done by tiny cameras in the rafters of a number of NBA arenas.

Those cameras are part of a system called SportVU, and it has the potential to change everything we know about analyzing NBA basketball.

“This is everything we’ve been charting, all-encompassing, and so much more, and it’s all sortable,” says one Eastern Conference executive. “This isn’t something I ever thought possible.”

It was used by ten teams this season -- up from six last year and four in 2009-10 -- and with a third of the league now using SportVU and sharing data with each other, we can begin to draw conclusions about areas of the game previously left up to conventional wisdom.

SportVU tells us, with relative certainty, which player has the fastest top speed in the NBA. It tells us not who scores the most, but who scores the most per touch. It tells us who dribbles the most per game, and who dribbles the most compared to how many shots they take. And that’s just the surface.

If you’re wondering, the leaders in those stats -- and many more -- are dispersed throughout the words below.

Some of this data’s useful. Some of it isn’t. Some confirms conventional wisdom, some challenges conventional wisdom. But it’s all fascinating.


If you’re wondering about how serious this system is, know this: This is technology that was originally made for military use. SportVU was created in 2005 by Israeli scientist Miky Tamir, whose background is in missile tracking and advanced optical recognition. He used some of that same science to track soccer matches in Israel, spitting out similar fitness and movement stats now being tracked in the NBA.

The American company STATS purchased SportVU in 2008 and turned its focus to basketball. Soccer’s a second-tier sport in America, baseball was already in a statistical revolution of its own and football had too many players and not enough flow (although the leaders at SportVU haven’t ruled out pursuing the NFL).

With constant movement, a controlled environment and only 11 moving parts, NBA basketball was perfect.

So STATS, led by vice president of strategy and development Brian Kopp, sought out the most tech-savvy NBA teams for a test run during the 2009-10 season. He convinced the Dallas Mavericks, Houston Rockets, Oklahoma City Thunder and San Antonio Spurs to be the systems’ guinea pigs. The next year, the Boston Celtics and Golden State Warriors jumped in.

This year, ten teams’ arenas were fitted with SportVU: Boston, Golden State, Houston, Milwaukee, Minnesota, New York, Oklahoma City, San Antonio, Toronto and Washington. And that number is expected to grow into the teens next year.

How does it work?

There are six computer vision cameras set up along the catwalk of the arena -- three per half court. These cameras are synched with complex algorithms extracting x, y and z positioning data for all objects on the court, capturing 25 pictures per second.

Each picture is time-stamped and automatically processed by a computer, which connects the data to the play-by-play feed and delivers a report within 90 seconds of a play. This is the part of the process the STATS people are so proud of – the proprietary algorithms in the software, which they call the ICE Platform.

Almost instantly, coaches and stat guys have this information at their disposal on their computer or iPad.

They don’t always know what to do with the information -- yet -- but they have it.


Think of a stat within the boundaries of a game. Seriously. Any stat. Doc Rivers tried. He asked the Celtics’ stat guy, Mike Zarren, what the Celtics’ offensive efficiency was when Rajon Rondo held the ball for more than five seconds on a possession. At the time, Zarren didn’t know. Now he knows.

SportVU tracks every player movement, every pass, every shot, every touch -- everything. At this point, it tracks more information than teams know what to do with. Every executive interviewed for this article agreed they weren’t even using 10 percent of the information this system could provide. And they all agreed this is the future of advanced basketball analytics.

Here are a couple facts we learned from SportVU from this season:

* Paul Pierce averaged 4.5 assists this season, which is pretty good for a scoring wing. But that number doesn’t tell the whole story. According to SportVU, Pierce’s teammates shot a higher percentage after his passes than any other player in the NBA. This shows Pierce is passing at the right time -- he’s giving his teammates mostly layups and open shots.

* Nikola Pekovic’s breakout season was largely helped by Ricky Rubio. Pekovic made 76 percent of his field goals off Rubio passes, compared to 56.4 percent overall.

* The NBA-wide shooting percentage is significantly higher when the shooter doesn’t take any dribbles. This confirms what any basketball observer suspected: ball movement equals offensive success.

How do teams use this information? Well, that depends on the team, depends who you ask and depends what they’ll tell you.

“A lot of this stuff, because it’s brand new, they don’t want other people to figure out how they’re using it,” Kopp says. “We know they’re using it, but it varies by team. Everyone’s still figuring out the best way to use it.”

It’s competition. The executives interviewed for this story spoke slowly and cautiously, careful not to share anything with the teams trying to beat them.

A Western Conference executive said, frankly, “We know what we’re doing with it, but we don’t want other teams to know what that is.”

The potential benefits to coaches and observers is apparent, simply by taking a look at what the system can tell us about the basic areas of basketball.

Shooting: Shoulders square. Elbow in. Flick the wrist. Don’t force it. That’s what shooters have always heard from their coaches. With SportVU, coaches can track things like a player’s shooting arc on made shots vs. missed shots, or shooting percentages off the dribble or off the pass (hint: it’s always better off the pass). They can learn Shane Battier should only shoot threes from the corner, while Dirk Nowitzki shoots better from the wing and top of the key.

Rebounding: Throughout the history of basketball, the players considered the best rebounders were the players who averaged the most rebounds per game. But that doesn’t tell the whole story. What if there’s another elite rebounder on a player’s team hogging all the rebounds? Or what if a guy plays for a bad defensive team that doesn’t produce as many missed shots? SportVU allows teams to deeply analyze rebounding by generating never-before-seen stats such as rebounding chances (described as when a player is within 3.5 feet of the ball and, yes, that measurement is exact) and rebounding in traffic (when opponents are within that 3.5 foot circle).

Passing: It’s tough to analyze passers from team-to-team because two players can be in such different situations. Maybe Steve Nash was a better passer than Rajon Rondo in 2012 -- although that’s like picking between the cheerleading captain and dance team captain -- but Rondo has better teammates who hit a higher percentage of their jumpshots, which leads to more Rondo assists. But SportVU provides statistics that give context to assists, such as total passes, secondary assists (if Derrick Rose passes to Joakim Noah who quickly finds a wide-open Carlos Boozer under the hoop for a layup, Rose would receive a secondary assist), and shooting percentage after a particular player’s pass.

Athleticism: Perhaps the most revolutionary part of SportVU is its ability to measure players’ speed and leaping ability within an actual game. It can tell how quickly a player closes out on a shooter, or if he’s running full speed down the court. Pace is traditionally measured by the amount of a team’s possessions, but now teams can find out literally how quickly they’re getting the ball up the floor and learn exact time of possession stats.

Fitness: Body language usually tells coaches what they need to know about a player’s fatigue level, but that can be misleading. These days Tim Duncan looks like he’s rushing to the front of a nursing home cafeteria line while getting back on defense, but he’s still putting up double-doubles and controlling the paint. With SportVU, teams can learn a player’s average speed, so they can judge his fatigue level based on movement, not if there's color in his cheeks. And say a player is coming off a knee injury. Doctors could limit him to running two miles during a game, rather than giving a minute limit, which is a bit ambiguous in terms of how much stress is being put on a knee.

And, again, all of this is in the early stages.

Like when Harvard students were toying with home computers in the early 1980s, there’s no telling where this player tracking technology might take basketball analytics.


Many teams have turned Kopp down when he made his pitch.

Some teams don’t see a use for it right now. Other teams think it’s too expensive (SportVU costs “mid-five figures to low-six figures per year,” Kopp says, or about $8.8 million less than what Lamar Odom made this year). One team, the Mavericks, stopped using SportVU this year to use their own system (which many believe tracks similar data to SportVU, but Dallas won’t share).

But STATS is still meeting and working with the teams it doesn’t have.

“The best thing for me to do is show them data of their own players, and they’ll ask, ‘How do you have this?’” Kopp says. “Besides Dallas this year, there hasn’t been anybody that said no. They’ve all said something like, ‘We’re not ready yet.’”

The ultimate goal -- and wide belief -- is the NBA will purchase the technology and the data will be available to all teams and broadcast networks.

And that could lead to even more changes in how we view basketball.

For instance, the box score. Right now a box score isn’t of much use to NBA statheads. Besides the addition of plus-minus and shot attempts blocked, the NBA box score hasn’t changed for decades. And simple totals of points, assists, rebounds and the like don’t tell the whole story.

That’s why those assistant coaches are scribbling on their clipboards during games.

When this information becomes widely available, that’s when things will really start changing from the box score to advanced scouting to MVP voting.

“We need all 30 teams to get a true gauge on some of these statistics,” says Matt Bollero, a basketball operations assistant who works with SportVU for the Timberwolves. “Until we have 30 teams, we still think we’re in the 5-10 percent range of what we could be doing with this. It’s a really neat system and it’s really going to change the game. But until we get to that point, it’s just a great thing to envision.

At the very least, it’s a lot more than what fits on an assistant coach’s notepad.