The No. 1 seed Cleveland Cavaliers lost in catastrophic fashion Tuesday night to fall behind 0-2 in their second-round playoff series.

The second-seeded Celtics studied Cleveland’s mistakes as they looked to avoid the same fate.

Boston guard Payton Pritchard said watching the Indiana Pacers rally from seven points down in the final minute to stun the Cavs served as a reminder to never lose focus until the final buzzer sounds. The Celtics did just that one night earlier, blowing a 20-point third-quarter lead at home in a 108-105 overtime loss to the New York Knicks in Game 1 of their series.

“It’s really a must-win game. We know that,” Pritchard said before Game 2 on Wednesday night at TD Garden. “We’ve got to take care of home court tonight. So I think we’ll come out with a lot of energy and stuff like that, especially after watching the Pacers-Cleveland game. It’s a full 48-minute fight tonight. We let our foot off the throttle last game up 20. We let that one slip, so we can’t let stuff like that happen.”

The Cavs led the visiting Pacers by 20 midway through the third quarter, and two Donovan Mitchell free throws put them ahead 119-112 with 57.1 seconds remaining. Indiana then proceeded to close with an 8-0 run, capped by Tyrese Haliburton’s game-winning step-back 3-pointer with one second to play.

“You can learn from the people around you, so you can definitely learn from the Cavs,” Pritchard said. “Being up seven, the game’s never over ’til it’s over, so you’ve got to take care of the rock. And even on a free-throw box-out — all the little things matter, and we’ve got to learn from that and take it into this game.”

A failed free-throw box-out ignited the Pacers’ rally. Former Celtic Aaron Nesmith barreled in from beyond the 3-point arc to slam home a putback dunk, cutting Indiana’s deficit to five with 47.2 seconds left. That play seemed to be a point of emphasis for Boston head coach Joe Mazzulla the following morning, as Pritchard mentioned it multiple times during his shootaround news conference.

Haliburton’s game-winner also came off a missed Pacers free throw.

“We always look at stuff across the league — little plays, stuff that could come up in situations for us,” Pritchard said. “It’s just preparation at the end of the day, so if we’re in a situation like they were in, we’re already prepared. What are we going to do? How are we going to try to box these guys out? A free-throw box-out. And if I’m not in the lane, I’m boxing out outside the 3-point lane, I’ve got to hit a guy. Like, Josh Hart, he might crash hard, so I’ve got to be prepared to box him out in that situation. It’s the little things like that. You’ve got to just be a student of the game and learn and keep growing.”

Pritchard knew that a loss to the Knicks on Wednesday would put the Celtics — who never trailed in any series during their 2024 championship run — in a perilous position. They’d fallen behind 2-0 in a best-of-seven series 18 times in franchise history and went on to lose 16 of those. The lone exceptions: the 2017 first round against Chicago (won in six) and the 1969 NBA Finals against the Lakers (won in seven).

League-wide, teams that go up 2-0 in best-of-seven series have advanced 89.4% of the time (237-28).

The winners of Celtics-Knicks and Cavs-Pacers will meet in the Eastern Conference finals.

Porzingis returns

Kristaps Porzingis, who sat out the final two and a half quarters of Game 1 with an illness, was upgraded from probable to available ahead of Game 2. He did not occupy his usual spot in Boston’s starting lineup, however.

The Celtics instead chose to start Al Horford alongside Derrick White, Jrue Holiday, Jaylen Brown and Jayson Tatum.

Entering Wednesday, Porzingis had come off the bench just four times in his NBA career. Three of those came during last year’s NBA Finals, when Mazzulla opted to use the big man as an impact sub after he returned from multiple lower leg injuries.

Asked pregame whether Porzingis would have a minutes restriction against New York, the Celtics coach said: “Whatever gives us the best chance to win, that’s what we’ll do.”

Mazzulla revealed Tuesday that Porzingis’ ailment was connected to the viral illness that sidelined him for nine games in late February and early March.

“Since he came back, I think he’s been kind of dealing with it on and off, fighting through it, working through it, doing the best that he can,” Mazzulla said Tuesday. “I think it was just too much for him in that game.”

Porzingis has shot the ball poorly so far in the playoffs, making a team-worst 32.8% of his field goals and 11.8% of his 3-point attempts. He played 13 minutes in Game 1 and finished with zero points on 0-for-4 shooting.

Sam Hauser was downgraded from doubtful to out for Wednesday’s game as he recovered from the ankle sprain that knocked him out of Game 1. The bench sharpshooter also has been quiet this postseason, totaling 16 points (the fewest of any rotation player) over six games. Mazzulla kept him on the bench until the third quarter Monday night.

Hauser did some light on-court work at Wednesday’s morning shootaround but mostly stayed stationary while reporters were present. He and Porzingis were the Celtics’ two most efficient 3-point shooters during the regular season, converting at 41.6% and 41.2%, respectively.

Another Holiday honor

One week after receiving the NBA Sportsmanship Award, Holiday was announced as the 2024-25 NBA Social Justice Champion for his work away from the court.

The winner of that award, which was first presented in 2021, receives the Kareem Abdul-Jabbar Trophy and a $100,000 donation to a cause of his choice. Holiday’s will go to the Jrue and Lauren Holiday Social Impact Fund, which has “distributed over $5.3 million in grants and delivered more than 400 hours of coaching and support to nearly 200 businesses across the U.S.” since its founding in 2020, per an NBA release.

“Since entering the league, Jrue Holiday has dedicated himself to helping others in their times of greatest need and pursuing a more just society for all,” NBA deputy commissioner Mark Tatum said in a statement. “The selflessness that defines his game is even more evident in the work he and his wife Lauren do off the floor to create more opportunities for a generation of youth who might have otherwise been overlooked.”

Mazzulla said he appreciates that the league has an award like this to spotlight players’ character.

“I think that’s something that the league has done a great job of over the last five, 10 years or so, understanding that these guys are more than just players,” he said. “They’re people, too, and it’s bigger than basketball. We’ve got a lot of guys with high-level character, and it’s great to see that get noticed. I’m happy for Jrue.”

Holiday also has received a pile of accolades for his on-court performance, making the All-Defensive first or second team in each of the last four seasons and six of the last seven. That streak will end this season, however, because the 34-year-old did not reach the 65-game threshold for qualification.