Nylon Calculus: Was the Rockets’ clutch defense meaningful or a mirage?

The Houston Rockets have been billed as one of the top challengers to the Golden State Warriors this season, and they looked the part on Opening Night — stealing a 122-121 victory when Kevin Durant’s buzzer-beater was (correctly) ruled to have come after the buzzer. The biggest question for Houston this season is how well Chris Paul and James Harden will be able to co-exist on offense. There was some functional friction between the two, although Paul was effective despite shooting poorly, but the Rockets other new additions — P.J. Tucker and Luc Mbah a Moute — were huge.

The Rockets were +20 in the 28 minutes Tucker was on the floor and he and Mbah a Moute were a combined 6-of-9 on 3-pointers, a mark that’s almost certainly going to regress once the sample extends beyond a single game. Both players are defensive specialists and their presence made a big difference for Houston.

The Rockets surrendered 120.7 points per 100 possessions to the Warriors’ offense but that number was just 105.7 when Tucker was on the floor and 107.5 when Mbah a Moute was in the game. Interestingly, this defensive presence was most pronounced down the stretch of the fourth quarter. In this live win probability graph from Inpredictable, you can see how Houston’s fortunes shifted once they started getting those fourth quarter stops.

This game featured four minutes of clutch time (less than five minutes left in the fourth quarter, neither team ahead by more than five points) and in that span Houston’s defense allowed 101.7 points per 100 possessions. That number would have ranked third in the NBA stretched across the entire regular season last year. Houston’s performance over this entire game against Golden State — 120.7 points per 100 possessions — would obviously have ranked last in the league by a mile.

There is an idea that has been floated that a team like the Rockets, with an elite offense, doesn’t necessarily need an elite defense. They need to be passable at that end, with the ability to kick things up a few levels in key possessions when the game is on the line. That’s how the Rockets won this game and it’s an enticing formula to assume they can hold.

Last season Rocket’s ranked second in offensive efficiency and 18th in defensive efficiency. Their defense was 4.8 points worse per 100 possessions in the clutch; they had a -2.5 per 100 possession point differential in the clutch and one just 23 of the 41 games they played in which included some period of clutch time.

The graph below includes every team from the past five seasons, comparing their regular season defensive efficiency with their clutch defensive efficiency.

There is a reasonably strong correlation between the two data sets (0.601), meaning teams that are bad on defense across the entire season are also generally bad in the clutch, and vice versa. Just 15 of the 50 teams in the bottom third of the league by defensive efficiency over the last five years improved their defensive efficiency in the clutch. Just five teams in that group improved their defensive by 3.0 or more points per 100 possessions (roughly double the improvement the league as a whole averages in clutch time).

Interestingly though, one of those five teams was the 2015-16 Rockets who surrendered 105.6 points per 100 possessions across the entire season but just 99.6 points per 100 possessions in the clutch. However, that team was also one of only five teams in that 15-team sample that finished above 0.500 and made the playoffs — the others were the Wizards, Bucks, Cavaliers and Trail Blazers, all last season. Of the group, only the Cavaliers were realistic title contenders and their defense was their clear weakness.

Next: Nylon -- Why Chris Paul and James Harden are so tough in the penalty

So, yes it’s plausible that the Houston Rockets could have a middling regular season defense but when that is significantly more effective in defending key possessions when the game is on the line. However, it’s not a common path to success and focusing on holistic defensive improvement is much more likely to yield success.