After third straight loss for Celtics, stumbles can no longer be discounted as a hiccup

NEW YORK — As the Celtics were getting drubbed by the Nets in the second half Monday night, a pocket of fans in Barclays Center’s second tier piled on by chanting, “Kyrie’s leaving!”

Kyrie Irving, who was on the bench wearing a sports jacket because a quadriceps contusion kept him out of this 109-102 loss, has given no indication he will stray from his proclamation that he will re-sign with the Celtics this summer. But when he made that statement before this season began, he probably did not envision a start like this one.

The Celtics’ loss to the Nets, their third in a row, dropped their record to 25-18. They are now seven games behind the first-place Raptors and, perhaps more alarmingly, 2½ games behind the fourth-place 76ers. If the season ended now, Boston would not even have home-court advantage in its opening-round playoff series.

The standings will be sorted out in due time, of course, but it has reached the point where the stumbles can no longer be discounted as a hiccup.

Boston was without both Irving and guard Marcus Smart (illness) on Monday, but it has thrived when undermanned before. In this game, it was walloped by a 22-2 run in Brooklyn’s 44-point third quarter.

The Celtics trailed by 27 with just under nine minutes left before crafting a comeback that at least gave them something to feel, well, not awful about. But for a team with championship aspirations, losing by 7 instead of 27 against the Nets is hardly cause for celebration. Still, they took what they could get.

“[We were] playing loose, playing free,” forward Jaylen Brown said of the comeback. “We’ve got to have each other’s back regardless. That last group, we turned and looked at each other and said, ‘Hey, man, we’re down, but let’s [expletive] play.’ ”

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— Boston Celtics (@celtics) January 15, 2019

Just last Wednesday, the Celtics overpowered the Pacers to stretch their winning streak to four games. This three-game trip against mid-level Eastern Conference teams offered a chance to build on the good feelings. But now the Celtics return home after falling to the Heat, Magic, and Nets, and they will face the mighty Raptors at TD Garden on Wednesday.

The good news is that a win would offer another opportunity to declare that a winning recipe has been found. The bad news is that those refrains have been so temporary.

“It’s tough to win four straight and then lose three straight,” forward Marcus Morris said. “I’d be lying if I said we knew our identity.”

In recent years, the Nets were relevant to the Celtics only because they bestowed one high draft pick upon them after another. But coach Brad Stevens has warned everyone that this team is different, and on Monday Brooklyn grabbed its first win over Boston since Jan. 2, 2016. The Celtics are now 10-13 on the road this year, matching their loss total from all of last season, when they were 28-13.

This game figured to offer a significant challenge without Irving and Smart. After the loss to the Magic on Saturday, Irving pointed to the inexperience of Boston’s young players as a reason for their stumbles. After Monday’s loss, Brown seemed to push back against the notion that the team’s youth is responsible for its ruts.

“We’ve just got to have each other’s backs at the end of the day,” Brown said.

“We can’t make comments. We can’t point fingers. We just have to continue to empower each other and have each other’s backs. If we don’t, if we start pointing fingers, everybody’s going to go into their own little shells. We’ve got to continue to play basketball. It starts from the top to the bottom. Not from the bottom to the top but the top to the bottom.”

Players said that Irving addressed the team in the locker room after this loss, telling them they need to play as hard during the entire game as they did during that fourth quarter.

Brown, whose playing time and shooting statistics have dipped this season, had 22 points on 9-of-18 shooting in 32 minutes. Jayson Tatum made 12 of 19 shots and scored a career-high 34 points, but he mostly shrugged off the scoring effort because of the circumstances.

“We just have to be better,” he said.

Brad Wanamaker, who has been used sparingly due to Boston’s depth, provided a lift off the bench with 13 points and four assists. But there were too many glaring holes elsewhere. Gordon Hayward was 1 for 6 and scored just 3 points, and Terry Rozier was 3 for 12, with three first-quarter turnovers.

D’Angelo Russell had 34 points for the Nets, including 18 during the powerful third quarter in which Brooklyn shot 65.4 percent from the field and outscored the Celtics by 23 points.

The Nets took their largest lead, 97-70, with just under nine minutes remaining in the game. Stevens went deep into his bench, seemingly understanding that the deficit was too large to overcome. But the Celtics clawed back and actually pulled within 105-98 on a Brown layup with 1:28 left. They had two 3-point attempts that could have made it a 4-point game, but both were off, and the improbable comeback fell short.

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach.