It came down to the final second. Jayson Tatum’s buzzer-beating layup lifted the Boston Celtics past the Brooklyn Nets in thrilling Game 1 playoff action Sunday afternoon.

Tatum’s last-second shot gave the Celtics a 115-114 victory and a 1-0 series lead after the Celtics had blown an 11-point lead in the fourth quarter. While Tatum got the basket and the heroics, the Celtics won the game in the third quarter on some heads-up basketball by Marcus Smart.

The Boston Celtics nearly reverted to their old ways

This was something the Celtics hadn’t done in months. Boston blew a double-digit lead in the fourth quarter but overcame it with Tatum’s late hoop.

Blown big leads were common for the Celtics in the early part of the season. During a November game at home against the Chicago Bulls, the Celtics saw their 19-point, third-quarter lead quickly evaporate. Chicago outscored the Celtics 39-11 in the final 12 minutes en route to a 128-114 victory. That game prompted Smart to call out Tatum and Jaylen Brown for not passing the ball.

In a January game against the New York Knicks, the Celtics blew a 25-point lead and lost when RJ Barrett banked home a three-pointer at the buzzer. After that loss, Celtics coach Ime Udoka questioned his team’s mental toughness. Since then, the Celtics have become a different team.

Sunday, however, it looked as if the Celtics were headed back to their old ways. After outscoring the Nets 35-24 in the third quarter to break open a 61-61 halftime game, the Nets took charge and quickly wiped out the 11-point deficit. Brooklyn led by as many as five points before the Celtics battled back.

Marcus Smart’s third-quarter effort was the key to the Boston Celtics victory

The Celtics/Nets game was everything NBA fans expected. It was heated. It was a back-and-forth affair throughout. After the first half, the teams found themselves deadlocked at 61-61.

Smart then gave the Celtics some breathing room and injected some additional life into the TD Garden crowd.

With his team ahead by four, Smart stole the inbounds pass after a Boston basket and increased the Boston lead to 69-63 on a left-handed dunk with 9:40 left in the third quarter. Thirty-one seconds later, he drained a three-pointer to build the lead to 72-63. Boston took a 96-85 lead into the fourth quarter. Without that cushion, the Celtics would be staring at an early deficit in the series.

The Nets battled all the way back, eventually taking a five-point lead, but the Celtics survived. Smart even said he felt as if the game may end up going the way it would have earlier in the year.

“(The win) was fulfilling for us,” Smart said during his postgame press conference. “Especially because of the way we started this year off. Those types of games we would have lost. We probably would’ve crumbled. For a moment there, it kind of looked like that was the direction it was going.

“The resilience that we have, the approach that we have, and the work that we put in to make sure that doesn’t happen, and just learning. Unfortunately, we had a lot of games to learn from with those types of incidents. Everybody did their jobs.”

An unselfish Smart led the way on the game’s final play

Tatum got the credit for the final basket, but it was Boston’s unselfish play that made it happen.

On the game’s last possession, Brown drew the defense with him as he drove the lane. He kicked the ball out to Smart, who finished with 20 points, six assists, and seven rebounds. Smart pump-faked, took a dribble toward the middle, and hit Tatum, who spun around Irving and hit a layup off the glass for the win.

Three stars touched the ball on the final possession. Boston got the best possible shot it could. Smart gave credit to Udoka, who let the team go without burning his final timeout. Then he also credited his teammates.

“Give credit to JB, you know, pushing the pace, drawing four, and then making the right read,” Smart said. “I’ve always been told that you have more time than you realize. When I caught the ball, if I was open, I was going to shoot it. Then I seen two guys fly at me, so I’m like I’ll take a pump fake.

“Actually, I was about to throw it to Al off the dribble, and I saw JT cut at the last minute. Just wanted to get the easiest shot we can. I found JT, ad he made a great play to get the ball on the glass and finish it.”

All statistics courtesy of Basketball Reference.

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