The drumbeat on the Houston Rockets summer has been that they may have gotten worse — losing two key defensive pieces in Trevor Ariza and Luc Mbah a Moute, and gambling on their ability to make those losses up at the offensive end with scoring and shooting contributions from a hopefully engaged Carmelo Anthony and a hopefully engaged Brandon Knight.
It’s hard to overstate how important the Rockets’ improvement at the defensive end was to their tremendous 2017-18 season. With the addition of Chris Paul, their much-ballyhooed offensive efficiency was just an improvement of 0.4 points per 100 possessions over the season before. Their defensive efficiency, on the other hand, improved by 2.6 points per 100 possessions, going from 18th in the NBA, to sixth.
Paul was obviously a piece of that improvement, as was the emergence of Clint Capela and more energy and attention from James Harden. But the driving factor, particularly in the playoffs when they threw up serious roadblocks to the Warriors offense, was the versatile, switchy trio of P.J. Tucker, Ariza and Mbah a Moute.
Tucker is still on the roster and will spend plenty of time sliding between bigs and wings on the defensive end. Anthony is probably better suited to defend 4s, but will be a downgrade in both effectiveness and flexibility, and newly signed Michael Carter-Williams may help a bit. However, a lot of responsibility for replacing Mbah a Moute and Ariza will fall to James Ennis, another offseason addition.
Ennis split last season between Memphis and Detroit and carries a reputation as a physical 3-and-D wing, who could theoretically duplicate some of what the Rockets are losing on defense. ESPN’s Tim MacMahon has already reported that Mike D’Antoni may be focused on using Ennis alongside Anthony off the bench, trying to pair a stronger defender with a weaker one.
https://twitter.com/espn_macmahon/status/1044965775554097152/photo/1
The problem with all this is that Ennis’ defensive reputation may be overstated. ESPN’s Real Plus-Minus rated Ennis as a strong defensive positive during the 2016-17 season with Memphis, but last season estimated him to be a defensive negative by about as large a margin as Mbah a Moute and Ariza were positives.
The table below shows each player’s DRPM, along with the percentage of their defensive possessions they spent matched up with each position. The last column, ORPM%, is the percentage of their defensive possessions where they were matched up with the opposing team’s best offensive player, as measured by ORPM.
Then there is the fact that Ennis hasn’t been as versatile as either of the other two wings. Mbah a Moute essentially spent twice as many possessions matched up with point guards and centers as Ennis did last season. Ariza wasn’t asked to stretch quite as much as Mbah a Moute no one on the Rockets spent more time defending the opponent’s best scorer, something Ennis didn’t have as much responsibility for last season.
It’s possible that these numbers simply represent a down season for Ennis, and that he appears less versatile because he was simply asked to do less in the schemes the Grizzlies and Pistons used last season. Still, defense is what made the Rockets special last season — they have been outscoring opponents for years and there are diminishing returns to how much more efficiency they can wring out of that end of the floor. Continuing to play like a top-10 defense is crucial to their championship aspirations and for that to happen, a lot is going to be asked of James Ennis.