LeBron James is largely considered one of the best NBA athletes of the past decade, consistently scoring about 0.8 points per minute in play (for comparison, Kobe Bryant scored 0.62 and Blake Griffin scored 0.63 in their last 55 games). He’s also one of the best-paid athletes, contracted for 24 million USD in the 2016-2017 season. Last year, Quora user Shane Hiller calculated that LeBron makes about $107 per second of gameplay. That’s a lot of money, and a good coach should try and maximize LeBron’s performance.
That performance maximization tends to result in LeBron feeling very tired at the end of games. While playing for the Miami Heat in 2011, he appeared at a post-game press conference and stated that “44 minutes is too much” and that he needed as much energy as he could get to finish games well. According to the athlete, his performance worsened as game time dragged on, and he frankly needed a break.
But is this at all true? Mathematically, it’s impossible for any NBA athlete to score fewer points in a single game if he plays 48 minutes rather than 40; the worst he could do is not score any points in the last 8 minutes. But is it possible for those final minutes to be much worse on average? That kind of hypothesis makes sense – exhaustion leads to a dip in performance. It’s likely that even the best athletes can be pushed to the point where they don’t take as many shots and fewer go in.
This 2015 report explored the exhaustion possibility, focusing on King James before briefly exploring other NBA athletes. It’s conclusion? LeBron does fine even when he plays really long games. I mentioned earlier that LeBron tends to score about 0.8 points per minute. Well here is a chart that shows his scoring compared to time played.
Do you see the very longest games out to the far right of the x-axis? Note that these ones fit right on the prediction line, even when they were removed from training data.
When a different regression model that favored curved lines was fitted to the data, not only did the data fare worse, it predicted a slight upturn after the 48th minute. The startling conclusion is that (1) LeBron James tends to score more points when he players longer in matches and (2) he shows no performance downturn as games stretch past 40 minutes. Later in the paper, the authors showed that their models could be fine-tuned to get correlation values above 0.76! That suggests a very high predictive accuracy of the model.
Possible confounding factors
This kind of result ought to be taken with a grain of salt. Data and statistics are, after all, just that. Real games tends to be more complicated than statistical models give them credit for. The dynamic between coach, players, and the opposing team all need to be taken into account. Here are some possible factors that can add detail to the above findings:
- Game-to-game exhaustion: In a regular season match, it’s unlikely that a single team would face several very challenging teams in a row. That means during a close match, the coach might demand more out of his top stars. If they don’t get a chance to rest afterward, it could affect their performance or even cause injuries. In order to test this factor, it would be beneficial to look at just data from the NBA Finals matches where nearly every game is very competitive. If LeBron plays long minutes in both Game 1 and Game 2, what is the affect to his relative performance?
- End game behavior: It’s likely that when a basketball player is exhausted, he’s going to play differently. That will often translate to a downturn in shot performance, meaning we ought to see that long matches have, on average, lower percentages of shots going in than short matches. It turns out that this kind of analysis has already been done, and it shows that LeBron mostly tends to move toward his overall average as games go on (see especially his field goal percent). Overall, there’s seemingly no correlation between his game time and shot accuracy.
- Coach’s intuition: a team is more than just five players and chances are that your sixth guy is better than your fifth guy when he’s wiped out. This means that LeBron’s consistent points/minute metric could be a result of the coach pulling him out the second that he sees him falter. This makes a lot of sense, too. As was stated before, King James scores about 0.8 pts/minute. But once he hits a wall, that might drop to 0.4, and the second his coach sees that, he’ll make a substitution. In this sense, no amount of data can determine what LeBron’s performance would be absent the coach. Something makes me doubt anybody could convince the NBA to force star athletes to play long games regardless of their exhaustion just to gather relevant data.
Have another explanation for these metrics? Please leave a comment below!