BOSTON -- Before the Cleveland Cavaliers put their perfect 15-0 start to the season to the test Tuesday night at TD Garden against the defending NBA champion Celtics, Cavs coach Kenny Atkinson was asked what he hoped to get out of the game.
"We want feedback," Atkinson said. "More feedback. Hopefully, we'll see this team down the road -- and down the road in an important game. On the other hand, I don't want to blow this game out of proportion. It's that balance, but it's more anxious to see where we are."
Atkinson got his wish. The result? Boston, despite a stellar push from Cleveland after halftime, had enough to hold off the Cavaliers 120-117, ending Cleveland's unblemished start.
"I'm happy how we fought back," said Cavs forward Evan Mobley, who finished with 22 points, 11 rebounds and 6 assists. "That was the main thing that I can be happy about. I feel like we didn't start the best. That was the main thing that really shot us in our foot. But overall, I feel like we played a pretty good game.
"I think it was a good test, and from what I saw out there, we could be anybody."
Cleveland didn't, however, beat Boston on this night. As a result, after spending almost an entire month with a zero in the loss column, the Cavaliers now are 15-1 thanks to a 33-point, 12-rebound, 7-assist effort from Jayson Tatum, one of six Celtics to score in double figures.
Boston was red-hot from behind the 3-point arc, going 22-for-41. That included 14-for-22 from deep in the first half, the best single half of 3-point shooting by the Celtics over the past 25 seasons (minimum of 20 attempts), according to ESPN Research.
And while Cleveland mounted a furious second-half comeback to cut a 21-point deficit all the way down to two points in the fourth quarter, the Celtics (12-3) eventually hung on to end Cleveland's unbeaten run.
"Yeah, we knew," said Celtics guard Derrick White when asked if there was extra excitement around this game. Not only was Cleveland's unbeaten mark on the line, but it also was vital for Boston's chances of advancing to the knockout rounds of the NBA Cup after losing to the Atlanta Hawks here a week ago in their first group stage game. "Everybody knew that they were undefeated and coming to our building. And also, it's an NBA Cup game, and we already lost one game. So, it was a really big game in that aspect. So, we were all aware."
If these teams meet again in the playoffs -- as they did in the Eastern Conference semifinals last season -- the matchup probably will be one split along the same battle lines as Tuesday's contest, with the Celtics trying to dominate the 3-point line and the Cavaliers attempting to do the same in the paint.
In this one, both teams got what they wanted. Boston controlled the 3-point line, as it often does, outscoring the Cavaliers by 36 points from deep. But Cleveland had its way inside, maintaining a 60-36 edge in points in the paint and grabbing 12 offensive rebounds.
It was a parade of trips to the rim by Cleveland in the third quarter, in particular, that allowed Atkinson's team to get back in the game, as the Cavs scored 22 points in the paint in the quarter alone -- as many as Boston had in the entire game to that point. That effort was led by Mobley, who used his size to repeatedly punish the Celtics down low when he found a favorable matchup to exploit.
"Man, big time," said Donovan Mitchell, who led Cleveland with 35 points and 8 rebounds in 40 minutes. "[Mobley] set the tone for us. But when he's in there and being able to create, dominate the way he did, that's what he does. And it's continuing to be aggressive, and that's just part of the process, continuing to get better and better.
"We saw this against [Boston] in the series last year. He's continuing just to grow and get better, and that's who he is."
At times, the game felt like a playoff atmosphere. Players from both sides threw their bodies around, though few calls were made in either direction in spite of it. A frenzied crowd enjoyed the hot start for the home team then appeared anxious as Cleveland clawed its way back into the fight.
Ultimately, though, it was Boston that made just enough plays down the stretch to hold off the Cavs, with Celtics coach Joe Mazzulla saying he was particularly pleased with the way Tatum and Jaylen Brown -- who dueled with Mitchell down the stretch in a highly entertaining back-and-forth -- managed the physicality of the matchup.
"Yeah, it was great," Mazzulla said. "I thought both of them handled the pressure and the physicality well. We played a little bit slower, but it was more important to get to the proper spacing. It was more important to get our drive-and-kick reads. And they did a great balance of handling the pressure, driving to attack, driving to get to the free throw line, driving to find guys. So, I hope teams continue to be physical, because it just gets us reps, and I thought they handled it really well."
The Cavaliers felt the same way about how things played out. No, they didn't win the game to keep their unbeaten streak going. But for a young team trying to make strides beyond where it ended last season, there were a lot of positives.
"Just that it's the group I thought we were," Mitchell said when asked what he learned about his team Tuesday night. "It's just a test. This is a big test. Whether you win, lose or draw, it's just a test; and obviously you want to learn through wins, but we lost tonight. But there's a lot we can take away from the good in the second half and a lot we can learn from the first half to get better at."