A closer look at the Boston Celtics’ defensive struggles

What happened to the Boston Celtics’ defense? Fatigue and injury play a part, but the opposition has learned to exploit their weaknesses as well.

The Boston Celtics head into the All-Star break after three straight losses, giving up more than 120 points in back-to-back games. The team still owns the best defensive rating in the league, but it’s clear that the opposition has a game plan to beat them.

Step one: Drive the ball. Step two: Drive again.

According to the NBA’s hustle stats, Aron Baynes has drawn the most charges of any Celtic with 13. The next two are Marcus Smart and Shane Larkin, who have taken 11 and six, respectively. It’s unpopular to use injuries as excuses these days, when lack of effort is seen as the utmost problem, but it’s important that we recognize that multiple factors can hold a team back, and those factors are often connected.

Smart and Larkin are always applauded for their effort on the court, so naturally it would be missed when they don’t play. If you care about numbers, the same can be said about defense.

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Without Smart, the Celtics are missing a player than can guard all five positions. The defensive scheme of switching everything simply does not cut it when a defender like Smart is replaced entirely by Terry Rozier. The return of Smart alone won’t fix every problem, but what we’ve seen recently has much to do with the defensive core of Al Horford and Smart being split up for too long.

Per Synergy, the Celtics are third in the league in defending spot-up shooters, second at defending pick-and-roll plays where the ball-handler tries to score, and fifth in stopping transition offense. This accounts for three most common types of plays the Celtics have to defend and about 50 percent of all possessions.

The next three categories, however, tell a much different story. The Celtics are just 18th in the league while defending in isolation, 23rd at defending post-ups, and 15th in the pick-and-roll when the roll man (usually a big) attempts to score. This only accounts for 14 percent of all defensive possessions, but is still indicative of what the team struggles with.

What does it all mean?

The good defense

Spot up: This is where having so many wings pays dividends. All that length and speed allows them to close out on shooters. Most of the credit here goes to Horford and Jayson Tatum.

Pick-and-roll ball-handler: Horford can read the offense like a book, and while the Celtics don’t have much rim protection, they do have a brick wall in the form of Baynes. If it’s not a full-speed drive, it’s hard to get by the Celtics’ bigs, especially for a guard.

Transition: All the athleticism means there aren’t many players who will get beat down the court. This is more of a hustle stat, and less dependent on cohesive lineups.

The bad defense

Isolation: There’s not a lot of muscle mass outside of a select few — Smart, Baynes, and Semi Ojeleye. Even Jaylen Brown, who is great at standing his ground, can be moved by a savvy isolation player. The rest are either undersized (Larkin) or too skinny (Tatum).

Post-ups: For all of the defensive merits, there is a lack of rim protection. Horford gets out-muscled by the bigger centers and Daniel Theis fouls too much.

Pick-and-roll, roll man: More of the same. You wouldn’t know it by watching Horford and Theis, but it’s hard to stop a center in motion, and near impossible to interrupt a lob pass to the stratosphere for DeAndre Jordan.

The verdict

The Celtics get bullied in a lot of one-on-one, in-the-paint scenarios. To say that Smart can help solve those problems would be stating the obvious, but doesn’t solve the issue of playing without urgency. It’s debatable whether or not Smart can solve that at all. While Smart is essentially the founder of the new-look Celtics’ defensive identity, he can’t mend the fatigue that leads to 20-point deficits.

Here’s what I know for sure: The Celtics don’t have the versatility to make lineups work without Smart. At this juncture, the Celtics have exactly two players on the roster that should be considered playmakers – Marcus Smart and Al Horford. The rest of the roster is evidently top-heavy in defensive specialists who struggle to score, mixed with run-and-gun guys who need somebody else to initiate offense in the half-court.

The thread that ties those two groups together is a distributor. Kyrie Irving is still finding his way in that regard, and, if we’re being honest, running Horford as a point guard doesn’t work as well as we had dreamed.

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The solution isn’t palatable to the fans that want nothing but excellence delivered straight to their eyeballs every game, but the team needs to get a little healthier, older, and bigger to patch the holes. It’s going to take some time. Remember, it took a decade to get the right pieces around Paul Pierce.