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The Bulls defense is a mirage, part deux

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Chicago Bulls v Portland Trail Blazers Photo by Alika Jenner/Getty Images

The Bulls have had an atrocious start to the season, to the point where a two-game win streak is notable. One thing that Jim Boylen has tried to tout in his self-inflating way is the team defense.

“We’re going to keep playing this way,” Boylen said. “We’re going to keep defending this way. And we’re going to keep getting better.”


“What are our options?” Boylen asked when questioned about the defensive scheme. “We can drop our center and not impact the ball, right? So, that would be criticized. We’re (15th) in defense. Do you think that’s a good defensive number for this group of guys? Do you think we’re playing hard defensively? I do.

That was on November 27th, two days after we last addressed this topic, pointing out that this “hard style” as Boylen calls it may be producing a ton of turnovers and a good defensive rating (points allowed per 100 possessions), but looking deeper exposes too many holes. Especially against not-awful teams.

In the time since, the Bulls defensive rating has only improved, up to 12th in the league after putting up a ~107 Defensive Rating against the Warriors, Blazers, and Kings, capped by a stout 97 DRtg over the Morant-less Grizzlies this week. They are still leading the league in forcing turnovers, and by an astounding margin, 5% over the 2nd-ranked team.

Before that Grizzlies game, Seth Partnow (formerly in the Bucks front office, now writing at The Athletic), had a really interesting look at this style (via), something he’s identified through a team’s proprietary data as “the most aggressive in the league”, while resolving “this peripatetic switching and doubling is cause for concern.”

Partnow used the public tracking data, with the caveat that it’s “a blunt instrument” (I have very low confidence in the Bulls investing in anything better), to try and see trends with a combined baseline of 1) proportion of overall movement over pace (i.e. trying to nullify distance traveled simply switching ends on the court) and 2) the opponents overall movement and that influence on the defense.

His findings?

Interestingly, and perhaps worryingly for the Bulls, of the six teams in the quadrant combining above expected movement and better than league averaged defensive rating so far, it includes the top four and five of the top six most fortunate in terms of opponent’s simply missing uncontested 3s.


The Bulls are currently third in opponent 3FG%, which includes opponent shooters hitting 2.4 percent fewer of their uncontested 3s than expected, the second most favorable differential of any defense in the league

And this was calculated before the Grizzlies came to town and opened the game going 0 for their first 15 three point attempts to finish 7 for 30 from behind the arc. Tracking the Bulls defense, 14 of these attempts were ‘wide open’ misses by Memphis.

Partnow’s conclusion:

Now, simply looking at this one measure does not in and of itself demonstrate luck/positive short term variance, but it perhaps does indicate how teams that “run around” on defense a lot are at the mercy of opponent shooting to a large degree. It’s a worry for Chicago and something to watch closely to see if its overall defensive performance dips as opponent shooting normalizes to a degree.

The Grizzlies team we saw at the Bulls home arena stunk, and this will partially ‘normalize’ by playing better opponents. The Warriors matchup tonight is against another dog, and Basketball-Reference’s strength of schedule ranking has the Bulls currently at 3rd-easiest in the league (and that’s without the benefit of getting to play the Bulls!).

One thing looks more certain: given his comments, even if Boylen sees the opponents open shots start to go in, he isn’t going to change the style. More than likely he’ll attribute it to not playing it hard enough.