Giannis Antetokounmpo, Bucks overpower shorthanded Celtics

Giannis Antetokounmpo (right) keeps Gordon Hayward from getting a good look at the basket while fouling him during the first quarter Friday at TD Garden.Matthew J. Lee/Globe staff

After games, NBA locker rooms generally open up to the media following a league-mandated 15-minute cooling-off period. On Friday night, after the Celtics suffered their third consecutive loss, a 120-107 setback against the Bucks, their locker room door remained shut 35 minutes after the game’s conclusion.

Inside, the team had gathered to have a discussion about what exactly was going wrong. Later, the players were reluctant to share details about what they had talked about, why they had talked about it, and how animated the talk had been.

“It’s none of y’all business, honestly,” Kyrie Irving said.

“It’s just something we’re supposed to keep in the locker room,” Jayson Tatum said. “It’s not for everybody to know what we talked about.”

“I’m going to keep it confined to between us,” Jaylen Brown said. “But it was well needed.”

But the snippets of frustration that the players revealed could be distilled down to a few simple points: The Celtics are not always playing with the effort and cohesion and consistency that they will need to make a deep playoff run. Irving even pointed out that there has been some “selfish play,” himself included.

“Much needed,” Irving said of the meeting. “Much needed. I think everyone can see that we’ve obviously had some inconsistencies regarding our play, so I think it was just time to address it.”

Despite the dour way the night unfolded for the Celtics, both on the court and off, the truth was that the Celtics were playing against the second-best team in the Eastern Conference, and Boston did not have three of its best frontcourt players: Al Horford, Marcus Morris, and Aron Baynes.

Still, coach Brad Stevens’s teams have thrived over the years when undermanned. Sometimes in these situations they have even used a lack of manpower as a motivator to play even harder. And that has not really happened very often this season.

“We just have to play harder,” Tatum said. “The last three games I don’t think we played as hard as we did the previous eight when we were winning.”

Kyrie Irving gains control of a loose ball from the Bucks’ Brook Lopez during the first quarter.Matthew J. Lee/Globe staff

The TD Garden crowd was as mercurial as the Celtics were on Friday night, alternating between frustrated boos and hopeful cheers before finally settling on resignation.

The undermanned Celtics fell behind the Bucks by as many as 26 points in the first half, and although there were lively moments went it felt as if an improbable comeback might materialize, it did not.

It was an odd game in several ways. The Celtics attempted a season-high 36 free throws and forced 21 turnovers while committing just five, but still trailed by double digits for the game’s final 37 minutes.

That was largely due to the presence of Giannis Antetokounmpo, the frontrunner for league MVP. The Bucks star had 30 points, 8 rebounds, and 5 assists, and he almost singlehandedly kept the Celtics at bay in the third quarter.

Brown snapped out of his recent funk with 21 points and seven rebounds, including a pair of emphatic dunks. But his night also including some puzzling moments, like a pair of botched fast breaks, an air-balled free throw, and a technical foul for flexing his muscles after dunking on Antetokounmpo when Boston trailed by 15 points.

With so many big men out, Stevens elected to use a smaller lineup featuring the 6-foot-7-inch Semi Ojeleye at center. The Celtics started the game on a 10-1 run in front of a lively, playoff-like crowd, but the night mostly went sour from there.

The Bucks called timeout, and then came back onto the court and seized control of the game with a powerful 16-0 run.

Midway through the second quarter, Eric Bledsoe hit a 3-pointer and then coasted to the hoop for consecutive layups. Antetokounmpo then put back his own missed shot, giving the Bucks a massive 58-32 lead. It was a 57-22 run since the start of the game, and it led to boos pouring down from the upper reaches of the Garden.

“I think we came out great on both ends, and we kind of relaxed, especially on defense,” Tatum said. “They got too comfortable.”

The Celtics’ Daniel Theis battles for a loose ball with a diving Eric Bledsoe during the first quarter at TD Garden.Matthew J. Lee/Globe staff

Boston pulled within 65-48 at halftime, and the third quarter was mostly the Celtics vs. Antetokounmpo. And he’s one of the few players capable of making that a fair fight.

He threw down a monstrous dunk, hit a 3-pointer, and converted a 3-point play, all while the Celtics were clawing back.

Antetokounmpo had 17 points in the quarter, including his team’s first 14. Boston pulled within 11 points several times but Milwaukee led, 93-78, at the start of the fourth.

With 9:47 left, Brown surged through the lane and through down a vicious one-handed dunk over Antetokounmpo. Brown stood and flexed his muscles as he stared at the Bucks star and was whistled for a technical foul.

But the play seemed to ignite Brown, who then drilled a pair of 3-pointers over the next two minutes, helping Boston pull within 103-92. But the run stalled there, and the locker room chat began soon after that.

“We need a few more [meetings],” Brown said. “We’ve got to keep going forward though, just keep building.”