Analyzing the Houston Rockets’ defensive changes

Where the Rockets’ have declined on defense

The most important metric for determining defensive success is opponent effective field goal percentage (eFG%). In a “make or miss league,” the defenses that make ‘em miss reign supreme. Last season, the top three teams in defensive rating finished one, two, and three in opponent effective field goal percentage. Unfortunately, this is where the Rockets have gone backward.

Last season, the Rockets’ opponent eFG% of 55.4% was 29th in the league. Essentially, every game, the Rockets’ defense allowed their opponent to shoot as efficiently as the Utah Jazz, who would ride an eFG% of 55.5% to the league’s number one rated offense. 

This season, things have gotten even worse. The Rockets are allowing an opponent eFG% of 56.3%. Interestingly, the league average eFG% has remained the same over the past two seasons at 53.2%. Season-over-season, the Rockets’ ability to prevent their opponents’ shots from falling has declined by 1.7% compared to the league average. With such a small sample, it needs to be explored whether the Rockets have been unlucky, or if something is structurally wrong with their defense. 

Analyzing the Rockets’ defensive shot charts

There’s some good news and some bad news regarding the Rockets’ defense. Let’s start with the good news. The Rockets are allowing a lower percentage of their opponent shots 0-to-3 feet from the rim than last season, going from 27.5% to 26%. This comes as the league is allowing a higher percentage of shots in the 0-to-3 feet range, going from 24.1% to 25.6%. Compared to the league average, the Rockets have seen their opponents’ attempts 0-to-3 feet from the rim drop by 12.5%. 

That is an incredibly promising development. Shots 0-to-3 feet are the most efficient shots in the sport. Preventing them is the number one goal of any defense, and in the early going, the Rockets are doing that. 

Unfortunately, the Rockets have seen a massive spike in the percentage of shot attempts 3-to-10 feet from the rim. The Rockets are allowing 21.8% of their opponent shots to come in the 3-to-10 feet range, a massive increase from 17.7% last season. Season over season, the Rockets have seen a 21.1% increase in shots 3-to-10 feet from the rim compared to the league average. 

The only area where the Rockets’ have seen a sizeable change compared to the league average are on shots 16 feet to the 3-point line (long-2s), but those shots make up a little more than 5% of their opponents' shot diet. In terms of opponent shot diet, the Rockets have improved their defense, so why are the shots falling more often?

The first issue is that the Rockets have been worse at defending shots 0-to-3 feet and 3-to-10 feet from the rim. They’re allowing teams to shoot 71.8% 0-to-3 feet, the league average is 67.5%, and 50.4% on shots 3-to-10 feet from the rim, when the league average is 44%. 

This isn’t a new issue, as last season they were worse than league average at defending these shots, but the degree to which they’ve struggled is staggering. Season over season, they’ve gotten 2.6% worse than the league average at defending shots 0-to-3 feet from the rim and a staggering 10.4% worse defending shots 3-to-10 feet.