It looked like the Celtics would suffer their first major loss of the season. Instead, they pulled off a huge comeback to force overtime. But in the end it was all for nothing. The Celtics lost an overtime thriller to the Pacers 135-132 on Wednesday in Indiana, suffering their first loss of the season. The Celtics fell to 4-1 on the season, while the Pacers improved to 2-3.

Initially, the C’s kept pace with the Pacers early, helped by a buzzer-beater from Derrick White late in the first quarter. But Indiana kept going in Boston and also handed the C’s their first double-digit deficit of the season. When the Pacers had a 24-point lead in the third quarter, they threatened to eliminate the defending champions.

But midway through the fourth quarter, the energy changed. The Celtics went on a 33–12 run to force overtime to stun the Pacers, erasing a 21-point deficit in less than nine minutes of game action. Neemias Queta gets partial credit for that run because he changed the equation with his play down the stretch. But the Pacers got Pascal Siakam’s game-winning 3-pointer in overtime to finally put the C’s to bed.

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Jayson Tatum led the C’s with 37 points and eight rebounds. Jaylen Brown had another 25 points, while Derrick White had 23. Siakam was huge with 29 points and 11 rebounds — especially down the stretch — for the short-handed Pacers, who were without big man Myles Turner. Benedict Mathurin had another 30 points.

The Celtics continue their road trip and will take on the Hornets for their next game in Charlotte on Friday at 7 p.m. Here are four lessons from Boston’s loss to Indiana:

Just briefly summarized: It looked like the Celtics were quietly going to suffer their first loss of the season. Even as they cut the deficit to 14 points, the Pacers continued to come at them early in the fourth quarter. Then some things changed for the Celtics. Queta’s energy was immediately noticeable as he was seemingly everywhere – this was reflected in the plus-18 on display in his 14 minutes. Queta also finished with two points and nine rebounds. The C’s also forced turnovers to put all the pressure on the Pacers. For the fight the Celtics missed early, they brought it late with some help from their bench guys. But they couldn’t finish the job as they lost for the first time this year.

Rotational wrinkles: When the Celtics made their huge comeback, it happened off the backs of some key players like Payton Pritchard and Queta. In particular, C’s coach Joe Mazzulla rolled with the boys lifting them up and giving them some life. Pritchard and Queta played through the extra period. Pritchard in particular clearly gained confidence as he finished after 39 minutes, scoring 16 points, four assists and four rebounds. As a bonus, Jordan Walsh also got a few stints playing eight minutes. That’s despite Sam Hauser returning from a three-game absence, so that’s a plus for Walsh seeing some game time.

Defensive test: While the Celtics were beating the Pacers in the East Finals last year, the young Indiana squad gave them fits. That was more of the same to start this season as the Pacers gave the Celtics all they could handle and then some. The Pacers were ruthless offensively and forced the Celtics back on their heels. Indiana finished with 62 points in the paint and 29 fast-break points. Those are the staples of this Pacers style, as they just kept putting the pressure on the Celtics. But the Celtics turned up their intensity during that fourth-quarter comeback, allowing just 12 points in the final 8:55 of the game to give them a chance.

Heavy shooting evening: While Brown contributed elsewhere, it was a tough shooting night for the All-Star. Brown finished 1-for-11 on 3-pointers as he cooled off after a hot shooting start. Tatum also went 5-for-18 on 3s, including a 1-for-7 start to the game. But Tatum was able to help his numbers by going 12-for-15 from the free throw line.