BOSTON — The Nets wasted a brilliant outing from Kyrie Irving and watched as Jayson Tatum stole Game 1 of their Eastern Conference first-round series. 

Tatum’s cutting layup, with Irving defending him, just beat the final buzzer and beat Brooklyn 115-114 before a sellout crowd of 19,156 that shook and rocked TD Garden. 

Irving had been unguardable in Sunday’s return to Boston, pouring in a game-high 39 points. But the Nets squandered it, in a heated matchup that featured the Celtics fans jeering and booing and cursing Irving from the start, and the All-Star giving them the finger after a third-quarter 3-pointer. 

“I wouldn’t say we’d like to avoid them in any way,” Irving said before the series. “This is the best part of the story that could be written. We go against Boston and have a chance to redeem ourselves [for a shaky regular-season]. They have a healthy team, we have a healthy team; now we get to see who’s [better].” 

On Sunday, the Celtics were one play better. 

Irving had carried the Nets back from a 15-point third-quarter deficit, and a nine-point hole in the fourth. He gave them a 107-102 lead with 5:30 to play, but they couldn’t hold it. 

Boston closed on a 13-7 run. 

With the game knotted at 109-all, Kevin Durant (23 points) got a shooter’s bouncer on a 13-foot baseline turnaround with 1:20 to play. 

Boston big man Al Horford’s put-back pulled the game even with 59 seconds left. But Irving drilled a huge 3-pointer 14 seconds later, sending the Celtics into a timeout. 

Jaylen Brown’s layup cut Brooklyn’s lead to one with 38 seconds remaining, and, after Durant missed a forced 3-pointer as the shot clock was expiring, Tatum (31 points) did the rest. 

“Yeah, you know, at that point, it’s a little bit random,” Steve Nash said. “They pushed it instead of calling a timeout. I think we took away the first action with Brown, went to [Marcus] Smart. 

“I thought we were intelligent on that side of the action, but he got into a crack and somehow found Tatum, who made an intelligent cut. So you know, split second here and there and the game goes the other way.” 

Nash didn’t think Irving would be impacted positively or negatively by the crowd reaction to his TD Garden return. 

“I’ve never really thought about it in those terms. You go and play ball and play hard and try to win the game. I don’t think you really worry about the fans,” Nash said. “The fans are part of the game. I feel like it’s such a part embedded in your career you don’t go into the game worrying about fans. 

“You go into the game worrying about performing. I don’t worry about Kyrie. Young players, they’re getting their feet wet in this scenario and some of that is a process. But once you’ve been there a few times, Kyrie’s been here a number of times. He’s been here proverbially in a playoff sense and hostile environments dozens of times. It’s not that I really think that has a huge effect on Kyrie.” 

It was still tied at 63-all a minute into the third quarter, before Brooklyn allowed nine unanswered points. Marcus Smart capped the Celtics spurt, and put Boston ahead 72-63. 

Brooklyn’s deficit swelled to 84-69 after Tatum’s free throws with 6:06 left in the quarter. The Nets still trailed 98-89 after Tatum’s free throw with 10:36 to play, but that’s when they rallied by ripping off 13 unanswered points. 

Irving brought them back, his layup pulling Brooklyn within 98-97. And after a frenzied sequence of bodies flying all over the court, the point guard found Durant for a go-ahead 3-pointer. 

Brooklyn led by two, and Irving’s layup pushed it to 102-98 before Jaylen Brown’s baseline dunk finally broke the Nets run. 

A Smart driving layup tied it again, at 107-all with 3:16 to play. That’s when the real drama started.