The Portland Trail Blazers defense has been remarkably better this season. Through four games they’re surrendering only 93.4 points per 100 possessions — the second best mark in the NBA. Quite the improvement for a team that finished in the bottom third last season.
The caveat is that the competition has been ...ahem... less than impressive, with only one of Portland’s four opponents, the Milwaukee Bucks, posting a winning record so far.
Which prompts the question: Is Portland’s defense actually THAT much better, or have they been feasting on weak opponents?
To answer the question, it might help to look at how the Blazers did against last season’s opponents. Were there specific styles of play that confounded them? So far, have they played against teams they struggled with last season?
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 offensive. 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 Lakers have a score of 9.86. That means they scored nearly 10 fewer points against Portland than the rest of the league over 100 possessions.
Shooting Efficiency and Offensive Rebounding Define the Blazer Defense
First of all, the Blazers have a positive rating against only 10 teams, meaning that most teams scored more than average. This is no surprise as the Blazers had a poor defense most of last season.
Beyond that, trends get harder to decipher. Three of the 10 teams the Blazers had a positive net rating against were in the top 10 for overall offense (Raptors, Timberwolves, Nuggets) and three were in the bottom 10 for overall offense (76ers, Hawks, Lakers).
But looking at Basketball Reference’s four factors does help paint a picture of last year’s defense. Here are the rankings for the teams the Blazers did the best and worst against last year:
At the extremes, turnover percentage and FT/FGA are roughly equal. This implies that forcing turnovers and giving up foul shots didn’t really help or hurt the Blazers too much last year.
Effective field goal percentage and offensive rebounding percentage, however, do differ. Teams that Blazers struggled against were ranked higher (average rank = 11.8) on eFG% than teams the Blazers did well against (average rank = 19.8), implying that the Blazers struggled more than most teams to defend efficient shooting.
ORB%, however, was the opposite teams the Blazers did well against ranked highly (average = 10.8) while teams they performed poorly against did not rebound well (average = 23.2). This implies that the Blazers defense neutralized offensive rebounding last year, giving them an advantage other teams did not have.
The last factor is Jusuf Nurkic. He appeared in games against eight of the 10 teams the Blazers fared the best against, but against only four of the teams they fared the worst against. His steadying influence as a defender around the rims seems to have paid dividends.
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 are very good or very bad at shooting efficiently and offensive rebounds. Indeed, the team’s only loss so far has been against the Bucks, who rank No. 3 in EFG% and No. 30 in ORB%. Going forward, it will be interesting to see if the Blazers can maintain their hot streak on defense, or if they will falter as they play more teams similar to the Bucks.