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Analysis: Breaking Down the Blazers’ Improved Defense

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The Portland Trail Blazers have been elite defensively this season. What’s changed? Eric Griffith digs into the stats to look for answers.

Washington Wizards v Portland Trail Blazers Photo by Sam Forencich/NBAE via Getty Images

The Portland Trail Blazers have the No. 4 defense in the NBA, according to stats.nba.com. Quite an improvement from their No. 21 ranking last season! As the midway point of the season approaches, the sample size is getting large enough to examine the Blazers’ defense more closely, and draw conclusions about how they have improved.

In October, I analyzed which offensive styles confounded the Blazers’ last year, and concluded that efficient shooting gave Portland more trouble than other teams. Today, I’m repeating the exercise to help parse what has led to the defensive resurgence.

Assessing the Blazer Defense, Relative to the Rest of the League

Rather than looking at straight defensive rankings, I propose that we consider how the Blazers did relative to the rest of the league. For example, everyone knows the Warriors have a really efficient offense. Seeing that they torched the Blazers doesn’t really help us because the Warriors torch nearly everyone.

But are there specific teams that the Blazers held well below their average, and do those teams have any commonalities in style of play?

Here’s a table breaking down that question:

To construct the table I took the opponents’ overall offensive rating, removed games played against the Blazers to get their rating against the rest of the league, and then compared that to how they did against Portland. The key column is on the far right (“Difference”). A positive number indicates that the Blazers held that team to fewer points than the rest of the league on average.

For example, the Suns have a score of 16.0. That means they scored 16 fewer points over 100 possessions against Portland than the rest of the league. Conversely, with a difference of -15.1, we can determine that the Cavaliers scored much more against the Blazers than they have against the rest of the league, on average.

Free Throws and Offensive Rebounding Define the Blazer Defense

First of all, the Blazers have a positive rating against 16 of the 26 teams they’ve faced, meaning that most teams scored less than average. This is no surprise as the Blazers have a highly ranked defense, and is a nice contrast to last season where only 10 of 29 teams had a negative rating.

Beyond that, trends get harder to decipher. Three of the nine teams the Blazers performed best against have highly ranked offenses (Raptors, Pacers, Nuggets) and two were poorly ranked (Magic, Kings). Similarly, two of the teams they were worst against are strong offensively (Rockets, Cavs) and two are weak (Nets, Bulls).

But looking at NBA.com’s four factors does help paint a picture of the defense. Here are the rankings for the teams the Blazers have done the best and worst against:

Turnover percentage is roughly equally in both good and bad games for the Blazers, and near the league average, so turnovers do not appear to be a strength or weakness for the defense. Conversely, the Blazers have performed well against good offensive rebounding teams, suggesting that Portland has done a good job of neutralizing rebound advantages.

Teams that shoot a lot of free throws have generally played well against the Blazers this year. Removing the outlying Bulls game, and teams that have given the Blazers the most trouble have a free throw rate rank of 5.8, while teams the Blazers have played well against have an average rank of only 13.6. Similarly, if the outlying Bulls game is removed, the Blazers have played poorly against teams with a high eFG% ranking (average rank = 11), but have played well against teams with a poor eFG% (average rank = 21.4).

In short, teams that get to the line a lot and shoot efficiently cause more trouble for the Blazers than for most other teams, but Portland is more equipped than most teams to take advantage of opponents that shoot inefficiently.

What does that mean for this year?

To truly understand how much better Portland’s defense has gotten this year it’s worth paying attention to teams that shoot efficiently and draw lots of foul shots — those are the opponents most likely to give the Blazers trouble. On the other hand, Portland has excelled at minimizing the negative impact of opponents’ offensive rebounding and exploiting teams that shoot inefficiently.