Kristaps Porzingis waved his finger to express his disagreement, walking away with a sarcastic smile on his face. On the bench, Jayson Tatum held both his hands on his head, incredulous at what he just saw.

The Celtics certainly did not agree with the call, or the other unfortunate officiating decision that led to this moment. But on a night in which their defense cost them, they had no right to complain. They went down in fitting fashion on Monday night in Indiana.

With the game tied in the final seconds, Bennedict Mathurin put up a 3-point prayer at the buzzer that missed. But the whistle blew. Porzingis made contact on his arm. The Celtics did not have a challenge remaining, and with 0.6 seconds remaining, Mathurin made two free throws that sent the Pacers to a wild 133-131 victory.

Jaylen Brown scored a season-high 40 points to lead the Celtics, who were still left puzzled at another call that cost them in the waning moments. On the previous possession, Brown dribbled into the corner in triple coverage against the Pacers and pulled up for a long two. Initially, it looked like he and the Celtics caught a break as Buddy Hield was whistled for a shooting foul after swiping him from behind.

But the Pacers challenged the call, and surprisingly, it was overturned. Though it appeared Hield hit Brown in the head, officials ruled that he made contact with the ball first, and gave the Pacers possession with two seconds remaining.

Though the Celtics were displeased with the result of those final calls, there was no excuse for them letting it get to that point. Tyrese Haliburton went down with an unfortunate hamstring injury late in the first half, but the Pacers still managed to thrive without their All-Star guard. After leading by nine at halftime, the Celtics gave up 74 points in the second half, including 44 in another bad third quarter with a brutal defensive showing.

Hield reportedly told Joe Mazzulla after the game that he did indeed foul Brown on that play, according to reporters in Indiana. But this game was lost before then.

“Close games, like we always talk about, they aren’t necessarily won in the last few minutes,” Mazzulla told reporters. “We took the lead, up two, battled back. But that third quarter, they just played with a little bit of inspiration, almost.”

Haliburton went down with 3:10 remaining in the second quarter, when he slipped while driving and made a split. He was in obvious pain, and needed to be carried off the court and into the locker room by two Pacers teammates, with his face buried in a towel, in an unfortunate scene. He was later ruled out with a hamstring strain. His teammates seemed shell-shocked following the injury, and the C’s took a nine-point halftime lead.

But the Pacers looked rejuvenated coming out of halftime. Even without Haliburton – the engine of their league-leading offense – the Pacers played with some extra juice. They played faster and sharper than the Celtics, who may have relaxed after Haliburton’s exit. The Pacers went on a 24-9 run to start the third quarter to take the lead. The game was changed by T.J. McConnell, who’s always a constant energy spark off the bench and continued to be so with countless hustle plays and continuously organizing the Pacers well in transition.

The Celtics continued to, surprisingly, struggle at the free throw line in the third quarter, and the Pacers punished them with big plays and shots. They took a two-point lead into the fourth in their dominant third quarter behind McConnell. One sequence in the final minute of the third – when he deflected an inbounds pass from Brown off of Payton Pritchard out of bounds, then buried a jumper – reflected his impact.

“That’s what he does,” Mazzulla told reporters. “We mentioned that in both pregames where as good as the Haliburton minutes are, the McConnell minutes, they lead the league in bench points. Forty percent of their points come from the bench and just little plays, whether it’s knocking the ball out of bounds, whether it’s getting a loose ball, whether it’s deflecting a pass or right-hand drive, so I thought that whole second half came down to the third quarter. We just have to play better.”

Mazzulla said there was nothing different about the third quarter except for the Pacers’ increased effort.

“Pure emotion,” Mazzulla said. “Pure hustle.”

The Celtics stayed tight with the Pacers throughout the fourth quarter. But they simply couldn’t get a stop. Mathurin and Hield each buried two triples in the final five minutes, and Aaron Nesmith’s three-point play – in which Brown was late on a defensive rotation – gave the Pacers a five-point lead with 2:23 to go.

The C’s responded with a 7-0 run behind Brown, who made two buckets before finding Porzingis for a 3-pointer that gave them a two-point lead with a minute left. But McConnell answered with a game-tying layup before the teams exchanged misses, leading to the final sequence that went sideways for the Celtics.

After Mathurin missed the last of his three free throws, Al Horford corralled the rebound and the C’s immediately called timeout. But the officials only gave them 0.3 seconds, which isn’t enough time to catch and shoot. They put their three tallest players – Porzingis, Horford and Luke Kornet – into the game in an attempt for a miracle tip-in, and Kornet nearly tipped in Derrick White’s inbounds volley to the basket.

But it should not have gotten to that point.

“We all have to be better on defense,” Mazzulla reiterated. “No 25-point quarters and a 44-point quarter isn’t good enough for us to win, so we all have to be better in that.”

…

Tatum missed Monday’s game due to left ankle sprain management, likely to give him a quick rest in the midst of a challenging portion of the Celtics’ schedule that includes a home-away back-to-back on Wednesday and Thursday against the Wolves and then the Bucks. Sam Hauser also missed Monday’s game due to a right shoulder impingement.