Put an End to Your Bets on NBA Head Coach, Gregg Popovich

NBA head coach Gregg Popovich of the San Antonio Spurs received the award for the third time on Tuesday. To some extent, these awards are intended to recognize the coach who has demonstrated the most willingness to willinggo above and beyond: They are the polar opposite of coach firings, which can be predicted more accurately by a coach’s performance during the preseason over/under lines in Las Vegas than by the coach’s win-loss record. The oddsmakers predicted that Popovich’s Spurs would win 55.5 games during the regular season, but they won 62. That is an admirable accomplishment, but it pales in comparison to Jeff Hornacek of the Phoenix Suns, who finished second in the voting after winning 27 more games than Vegas predicted. 

Even more incredible is Popovich’s and the Spurs’ ability to defy even the most persistently high expectations. From the start of the 2006-07 season to the end of the 2013-14 season, the Spurs outperformed the preseason over/under lines by a total of 35.5 games. That is the second-best total in the NBA, trailing only the Suns, who have benefited greatly from their outstanding play this season. It comes despite the Spurs being projected to win 53.2 games per season during this period, which would be the highest figure in the league. (These figures include the 2011-12 season, which was cut short due to labor disputes; as a result, the total number of games has been adjusted to 82.) 

Popovich was named Spurs head coach at the start of the 1996-1997 season. I wanted to compare his performance to the preseason over/under line from earlier in the season, but I couldn’t find any reliable numbers. There are, however, records dating back to the start of Popovich’s tenure that show how the Spurs performed against the point spread in individual games. When measured against this standard, Popovich’s performance is equally impressive. 

The Spurs’ win-loss record against the spread since Popovich took over as head coach is detailed in the table below. It includes both regular-season and postseason games; however, there are a few regular-season games from his earlier seasons that are not included. Popovich has a point spread record of 843 wins, 728 losses, and 32 draws in the total number of games for which we have data. If the possibility of a push is excluded, that equates to a winning percentage of 53.7 percent, a rate of success that all but the most skilled sports bettors in the world would struggle to maintain. 

How likely is it that Popovich’s success is due to pure chance? We will be able to test this hypothesis using a binomial distribution. If Popovich were only a.500 coach against the spread, the chances of him going 843-728 or better against it is only 0.17 percent. This is because Popovich is only a.500 coach against the spread. To put it another way, there are a lot of games, and Pop has done exceptionally well. There is a good chance that something is going on and that something has been missed by the betting public. (And it’s something it’s consistently lacked; Popovich’s edge hasn’t waned in recent years.) Against the spread, the Spurs have a 54.5 percent winning percentage over the last five seasons. 

I looked into a few different hypotheses. For example, the Spur Spurs’ success against the spread could be attributed to small-market teams rather than anything Popovich has done. There is a slight inverse relationship between team performance against the point spread and market size, which may account for a very small portion of the overall variance (meaning that teams in smaller markets tend to do a bit better against the spread). However, the effect is minor; it is enough to explain why the Spurs have won 50.4 percent of their games against the spread, but not even close to 53.76 percent. 

There is also the possibility that the Spurs have a pattern of poor early-season performance, which lowers bettors’ expectations. Following that, the Spurs may improve as Popovich evaluates and adjusts his roster’s strengths and weaknesses. That doesn’t quite work. The Spurs have a 53.5 percent point spread record in the first 20 games of the regular season dating back to the 1997-1998 season, which is roughly equivalent to their overall performance. (In the playoffs, they have a winning percentage against the spread of 55.9 percent, which is slightly better than their overall record.) 

Perhaps there is something peculiar about the Spurs’ point distribution. If they had an unusually high number of blowout losses for a good team, such as when Popovich rested his starters, this could artificially lower their average margin of victory, causing gamblers to underrate them in other matchups. 

The Spurs’ point distribution, on the other hand, appears to be relatively normal (both in the common language and mathematical senses of the term), and it also appears to be relatively symmetrical in terms of their average margin of victory. The Spurs have been less likely than the normal distribution would predict to win or lose games by exactly one point, but this is true for all NBA teams, owing largely to late fouling. The Spurs have been less likely than the normal distribution would predict to win or lose games by exactly one point. These are some of the possible explanations, which I don’t completely dismiss: The way NBA teams handle late-game situations has the potential to have a significant impact on both their scoring distribution and their ability to cover the spread. However, there is nothing about the Spurs that demands to be noticed right away. They have not been successful in winning more games than would be expected based on their overall scoring margin. 

There’s also the possibility that the Spurs, led by Popovich, have excellent “intangibles” that the betting public overlooks. There is no doubt that Popovich, like Tim Duncan, is an outstanding leader. However, those intangibles should eventually manifest themselves in the form of the Spurs winning more games than they would otherwise, and bettors should monitor the results and adjust accordingly. Those intangibles should eventually manifest themselves in the Spurs winning more games than they would otherwise. Furthermore, because of Popovich’s tenure with the team, the betting market may consider Popovich and the Spurs’ well-known reputation for strong coaching and veteran leadership. When asked to rank the best coaches in the NBA, general managers have consistently placed Popovich at or near the top of the list. 

I was curious to learn more about one of the data points in the absence of an explanation. Bill Belichick, the head coach of the National Football League’s New England Patriots, is the coach who most reminds me of Pop Warner. Belichick, like Popovich, appears to have an almost supernatural ability to make the best of any situation; for example, he coaxed 11 victories out of Matt Cassel. Belichick, like Popovich, is known in his field for being a brilliant and ruthless tactician. 

Despite the point spread, Belichick, like Popovich, has had a lot of success in his coaching career. Including his time as head coach of the Cleveland Browns, he has a lifetime record against them of 179-144-9, a winning percentage of 55.4 percent. (As head coach of the Patriots, he has a record of 138-106-6 against the spread, which equates to a 56.6 percent winning percentage.) 

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Referee Performance 

In this situation, I am aware of the possibility of confirmation bias. If you look for coaches who have a track record of exceeding expectations, you will most likely find that those expectations were met or exceeded in a variety of different data, including how they performed relative to the point spread. However, it is important to consider whether Popovich and Belichick’s coaching styles or some other aspect of their personalities are to blame for their ability to consistently outperform the oddsmakers. 

My response isn’t particularly enticing. I’m also not convinced that there is a seductive answer to this question. Popovich’s strong performance against the spread could be the result of a little bit of luck, a little bit of small-market bias, something funny about how the Spurs handle endgame situations, and a healthy dose of selection bias in our decision to examine his record (rather than that of other coaches) after the fact. All of these factors could play a role in Popovich’s success against the spread. But I have this idealistic picture of what might be going on here in my head. 

One thing that can be said about Popovich is that he has shown a remarkable ability to avoid regression to the mean. He adapts his methods and strategies to the situation at hand, keeping him one step ahead of his opponents. Under Popovich, the Spurs have been successful with both young and old teams, as well as teams that play quickly and teams that play slowly. Popovich doesn’t have many gimmicky qualities. 

Perhaps he has managed to keep one step ahead of Las Vegas by staying one step ahead of his competitors. It’s not just the fact that markets are already fairly efficient that makes it so difficult to make money betting on sports or engaging in any other market-based activity. It’s also the fact that even if you’ve discovered a market trend worth capitalizing on in the past, there’s a chance that other market participants have already done the same thing. You may have a temporary advantage, but it will not last forever. It will vanish quickly. Or, as in the game rock-paper-scissors, your opponents will exploit the fact that you are attempting to exploit them. 

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But what if your advantage isn’t in finding one specific market loophole, but in having the ability to constantly come up with new advantages? You should move on to the next tactic before your opponent figures out how to counteract the one you just used. Great poker players have the following abilities: They have an intuitive sense of when a specific strategy in a specific situation has transitioned from underutilized to overutilized in the poker “market.” They readjusted a fraction of a second before everyone else. 

My gut instinct tells me that the way skilled coaches like Popovich and Belichick exploit edges in their games is very similar to how skilled sports bettors exploit edges in their games. This is my romantic idea. As a result, the fact that Popovich and Belichick’s competitors have never caught up to either of them could explain why betting markets haven’t caught up to either of them. I am well aware that I would never bet on Popovich or Belichick to win. Furthermore, I would not want to play poker with them.