If you follow the politics of the NBA, a major issue you’d hear facing the league and commissioner Adam Silver is the volume of games played on back-to-back nights. Why is this important? Teams playing on the second night of a back-to-back series are notorious for underperforming due to fatigue off of only one night’s rest, and many fans and analysts view it as a competitive disadvantage. With players being more vocal about scheduling patterns and with the rising trend of players resting on the second game of back to backs, we’ll be seeing fewer of them this season; a drop from 19.3 to 17.8 per team on average, with no team exceeding 20 back-to-backs. In this post I’ll take a look at the statistical repercussions of teams playing the dreaded back-to-back games.
To the surprise of no NBA fan, teams playing on the tail end of a back-to-back win less frequently than teams who aren’t. Since the beginning of the 2013-14 season, teams on back-to-backs have a .444 win percentage compared to .517 otherwise. And while this discrepancy is partially explained by the fact that most back-to-backs end on the road (68%), teams win roughly 8% less often both at home and away.
Digging a little deeper, we can see the efficiency splits for back-to-back and normal rest games:
|Non-B2B games||B2B games||Difference|
Over the past 2+ seasons, teams tend to lose 2.21 points per 100 possessions in net efficiency on back-to-back games. A majority of that decline comes from the offensive end; teams playing on only one night’s rest score nearly 2 points fewer per 100 possessions than normal games. I took a look at Dean Oliver’s Four Factors (explained more in this post), plus assist rate (percent of field goals assisted on) and pace (number of possessions) to try and identify which part of the offense is lost the most on these types of games.
The first and third most important factors according to Oliver – Effective Field Goal Percentage and Offensive Rebound Rate – experience statistically significant drop-offs in production in the back end of back-to-backs, suggesting that a large portion of the decreased offensive efficiency is explained by teams shooting less efficiently and being less effective on the offensive glass. But the stat that suffers the most is the assist rate; the percent of field goals assisted on per game falls a full percent from 58.7% in full rest games to 57.6% in back-to-backs. Certainly more information can be gleaned from play-by-play data, but it may be fair to say that the added fatigue factor of back-to-backs discourages ball movement and hurts rebounding, a statistic typically attributed to hustle and energy.
For fun, here’s a look at the teams whose net efficiency fell the most on back-to-back games over the past 2+ seasons:
It should make sense to see that the Nuggets perform the worst on back-to-backs; if there is a real fatigue factor at play, you’d expect it to be more pronounced for a team who plays half of its games 5,000 feet above sea level. In fact, Denver has won just 2 of 10 such games at home over the past two seasons, compared to winning 55% of home games on normal rest. Expecting to see the Spurs here? Despite Gregg Popovich’s tendency to rest older players, San Antonio still won 70% of it’s back-to-back games in this time span, and shockingly rate as more efficient on the second night of back-to-backs.
Stay tuned for my next post, where I’ll look at the effect of back-to-back games on individual players.