Boston’s late-quarter issues hit their peak in the third quarter. After the Celtics took a 92-79 lead with 3:23 remaining, the Pacers nearly negated the deficit by the final buzzer of the quarter, making it a 94-93 game entering the fourth.

The Celtics outscored the Pacers by five points in the final two minutes of regulation, but Joe Mazzulla still wants to see his team execute better in the final moments before each end-of-quarter buzzer sounds.

“After losses in close games, I’ve said that the end of the game isn’t any more or less important than the beginning of the game,” the Celtics coach said on Wednesday, per Boston Globe reporter Adam Himmelsbach. “And so I’ll say it again, like, they outscored us by four at the end of the first quarter. They outscored us by 12 at the end of the third quarter. And so those are the things that you have to work on before you even get to that situation. And that’s why we were in that situation, because of the detriment at the end of the quarters, which is something that they take advantage of.”

Mazzulla estimated that 70 percent of the Celtics’ issues in Game 1 were execution-based, particularly on the offensive end.

The film would seem to back that up. In the first quarter, the Pacers turned a Jrue Holiday missed layup into two quick points in transition. A bad pass by the Celtics guard later turned into two more points for the Pacers before the end of the quarter. A pair of Al Horford missed 3-pointers in the final moments of the first and second quarters also led to relatively quick buckets for the Pacers.

The third quarter was especially egregious by the Celtics. Jaylen Brown threw a bad pass for a turnover, leading to a transition bucket for the Pacers. A Sam Hauser missed 3-pointer led to another transition basket for Indiana on the ensuing possession.

Payton Pritchard and Holiday each took 3-pointers relatively early in the shot clock on back-to-back possessions. Pritchard’s miss allowed Aaron Nesmith to leak out for a 3-pointer in transition while Brown rebounded Holiday’s miss, but only made one of two free throws after getting fouled.

An illegal screen by Hauser with six seconds left in the quarter allowed the Pacers to get an extra possession in the frame. They capitalized as Tyrese Haliburton hit a 28-foot 3-pointer off the backboard at the buzzer. Haliburton’s buzzer-beater at the end of the third came after he hit a 35-foot 3-pointer with under two seconds left in the second quarter.

While Haliburton’s shots quieted the TD Garden crowd on Tuesday, Mazzulla lamented over the offensive miscues made at the end of each quarter.

“I thought at the end of the first quarter, end of the third quarter, I think we had five turnovers, three or four of them live-ball, which gave them opportunities,” Mazzulla said. “I thought when we were spaced properly, when we had great screens, I thought we got really good looks.”

Those end-of-the-quarter possessions were obviously different than how the Celtics played in the opening minutes of each quarter. They took a quick 12-0 lead as they only committed one turnover in the first 11-plus minutes of the game. They only committed two turnovers in the first 11-plus minutes of the third quarter as well.

Mazzulla thought the Celtics’ “rim decisions kept [the Pacers] out of transition” early on, but their turnovers allowed them to get into transition easier. That’s why he’s emphasizing better offensive play in Game 2.

“Defending them starts with your offense,” Mazzulla said. “I know it’s counterintuitive, but you have to keep it 5-on-5. You look at the first six minutes of the game, every shot they took, with the exception of Nesmith’s missed layup, was in a 5-on-5 setting.

“So, you have to work to keep it 5-on-5. You have to do that with your offensive spacing, decision-making, and. Once it gets to 5-on-5, that’s where the individual accountability, the communication, and team defense comes into play.”