BOSTON — The Celtics have been many things this season.
Explosive from the 3-point line. Unguardable in transition. A nightmare for defenders, who have witnessed another leap in the twin-pronged development of Jayson Tatum and Jaylen Brown, two young players who, around this time last year, were coping with criticism about whether they could coexist. Now, they have the Celtics positioned as a presumptive favorite to return to the N.B.A. finals — and perhaps win it all.
Yet for all their pyrotechnics on offense, the Celtics have had their issues on defense. Through the early weeks of the season, Boston has been more pasta strainer than steel curtain when it comes to thwarting open looks. Considering everything else that the team can do — namely, score oodles of points — the Celtics have offered up some decidedly mediocre defense.
But that may be changing, which is awful news for the rest of the league.
Facing the Celtics last week, the Dallas Mavericks were trying to sustain a late-game surge when their All-Star guard, Luka Doncic, found a seam to the basket — only to have his finger roll rejected at the rim by Tatum. The Celtics came away with the ball and pushed it ahead to Brown, who sank a 3-pointer to seal the Boston win.
As that sequence was playing out, Tatum and Doncic were left in quiet conversation at the other end.
“I told him that I didn’t want him to dunk on me,” Tatum said later. “He looked at me and was like, ‘You thought I was going to dunk it?’ I was like: ‘You never know.’”
The Celtics, who have won 13 of their last 14 games to improve their record to a league-best 17-4, still have a middle-of-the-pack, bend-but-don’t-break defense under Joe Mazzulla, their interim coach. Their defensive rating, which is a measure of points allowed per possession, ranked 14th in the league entering Tuesday. But over their past eight games, the Celtics have produced a top-10 defense — a sign of growth as they lean into Mazzulla’s up-tempo style while compensating for the injury absence of Robert Williams III, their starting center.
“Our offense is so good that it hides some of our defensive flaws,” Marcus Smart, the team’s starting point guard, said in an interview. “But we’re continuously out here working, and it’s only going to get better with time.”
And it will presumably improve even more later this season. After Williams underwent arthroscopic surgery on his left knee in late September, the team said he would resume “basketball activities” in eight to 12 weeks. There are no certainties about his health, of course, but even if Williams were to return at less than full strength, his mere presence around the rim would help. Last season, he was named to the N.B.A.’s all-defensive second team.
In his absence, Smart, who is 6 foot 3, has spent more time guarding opposing centers than he would prefer. After he averaged 1.7 steals a game last season, when he won the N.B.A.’s Defensive Player of the Year Award, Smart is averaging just 1.1 steals this season, a dip that can be attributed to his playing out of position.
“Because I’m guarding the post so much, you don’t want to gamble too much,” Smart said. “It’ll be different when Rob is out there and I can gamble. But without him, I have to be solid for my team and control that back line.”
The Celtics were all about grinding opponents to smithereens last season, when they led the league in defensive rating. Ime Udoka, who was in his first season as the team’s coach, made defense his priority, and it was a winning strategy. In the playoffs, Boston advanced to the N.B.A. finals before falling to Golden State in six games.
Mazzulla, though, was made interim coach on the eve of training camp after the Celtics suspended Udoka for the season for unspecified “violations of team policies.” (According to two people with knowledge of the situation who were not authorized to discuss it, Udoka had a relationship with a female subordinate.)
But while Mazzulla was an assistant under Udoka last season, he has not tried to replicate Udoka’s approach. Instead, Mazzulla has done things his own way — by recognizing the team’s unique offensive abilities. Entering Tuesday, the Celtics were leading the league in scoring, 3-pointers, 3-point percentage and offensive rating.
It is also worth noting that, as a part of Boston’s off-season trade for Malcolm Brogdon, the Celtics gave up Daniel Theis, a defense-minded center. The trade, of course, was worth it: Brogdon, a point guard, has been terrific coming off the bench, and Theis has yet to play for the Indiana Pacers this season because of an injured knee.
In any case, the Celtics have essentially been daring opponents to keep up with them. Sometimes, Smart said, that may mean that the Celtics give up an extra offensive rebound or two as they look to break out and run.
“When you’re not really boxing out as much and having as many guys stay back, your defense is going to take a hit,” Smart said. “But we’re going to get it together.”
For his part, Tatum has clearly taken another step as a defender by averaging a career-best 1.2 blocks a game. He recently described himself and Brown as “two of the best two-way players in the league.”
Tatum left his imprint on the Mavericks last week. Late in the second quarter, Tatum raced in as a weakside defender to swat a layup by the Mavericks’ Dorian Finney-Smith. Tatum corralled the rebound, brought the ball upcourt himself and got fouled attempting a 3-pointer. He made all three free throws.
“That’s what’s going to make him an even greater player — being able to do it on both ends,” Smart said. “We know what he can do on the offensive end. Everybody knows. But it’s even more detrimental to a team when you’re locking them up.”
There are times, though, when it may not even matter.
On Monday, the Celtics hosted the Charlotte Hornets, an injury-marred team that has taken up residence in the Eastern Conference basement. With Brown and Al Horford sitting out the second game of a back-to-back, Mazzulla went with a deeper rotation. Blake Griffin, who had been collecting dust bunnies on the bench for nearly two weeks, made his third start of the season and scored on the team’s opening possession. The Celtics sank 10 3-pointers in the first quarter and led by as many as 30 points before halftime.
They were well on their way to another rout in a season full of them.