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What happens during crunch time

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The above collection of charts shows how the Houston Rockets perform on four metrics during “crunch time,” defined as the last five minutes of a game in which the Houston Rockets are behind by five points or less, or tied.

Technical details

On the x-axis are seven different periods of time. The first one, called “all,” shows performance in a metric for the entire game. The next six shows a team’s performance in a metric only when the team is behind by five points or less, or is tied, with a certain amount of time left in the game. The blue line represents the Houston Rockets. The orange line represents all teams. So, if we look at the first chart, it shows how the Houston Rockets and the rest of the NBA perform on defense in general, and how that performance changes when the game is close and less time remains in the game.

Important limitations

  • Because not all games are close, the sample size of the games (and possessions from those games) as one moves to the right in each graph becomes very small. 
  • The NBA average is an unweighted average. Each team’s performance is considered equally when calculating the average, regardless of how many crunch time possessions and games the teams played. For this reason, the NBA’s offensive and defensive ratings do not mirror each other.

Observations

All teams seem to do worse during crunch time. Considering this is when teams need to score/get a stop the most, it’s interesting that whatever it is they are doing is actually less effective than what they do during the rest of the game. The Houston Rockets are even worse during crunch time compared to NBA average. In each metric, the Houston Rockets see a greater decrease in performance relative to their overall performance than the NBA average.

The Houston Rockets offense, in particular, sees a stunning decrease in performance. In both offensive rating and true shooting percentage, the Houston Rockets are higher than the rest of the NBA over the course of entire games, but plummet during crunch time, dipping more and more below the NBA average as closely contested games near their conclusion. While the sample size is admittedly small, in the final thirty seconds of games in which the Houston Rockets are down by five or less, the offense is operating in a way that would extrapolate to 37 points per 100 possessions (compared to 85 for the entire league), with a true shooting percentage of 18% (compared to 38% for the entire league).

That the NBA’s assist ratio decreases as less time remains suggests that heroball is alive and kicking. That the Houston Rockets assist ratio decreases at a greater rate than the NBA’s as less time remains suggests that heroball is employed readily by the team. Since the offensive rating and TS% of the team also decrease over the same time periods, it might be time for the Houston Rockets to rethink their crunch time tactics.

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About the author: Richard Li is an independent researcher and consultant. He likes numbers and pictures.

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