BOSTON — Jayson Tatum is no stranger to closing games on the bench. He did it a bunch of times this season, almost always at the end of lopsided wins. For him, a seat on the sideline for the final seconds is usually like a victory cigar.

Not so Thursday night. Tatum watched the closing moments of the Boston Celtics’ 118-94 Game 2 loss from the end of the bench with a towel laying over his lap. He clapped when Jaden Springer swatted an Isaac Okoro layup into the crowd, but Tatum and the other starters were not on the bench to celebrate a big win. They were all yanked with 4:48 left near the end of a blowout loss, which leveled the Eastern Conference finals at 1-1.

“I just felt like that was the best thing to do at that particular time,” Celtics coach Joe Mazzulla said. “We have another game coming up soon.”

The Celtics were looking ahead to Game 3. For the second straight series, they dropped Game 2 at home to allow a lesser team to earn a series tie. The Boston crowd unleashed a round of boos during the fourth quarter, letting the players know what Jaylen Brown acknowledged later: It was an unacceptable performance. With a chance to take away the Cleveland Cavaliers’ hope, the Celtics instead let them build confidence. Boston took away nothing. The Cavaliers lived in the paint during the first half, then toppled the Celtics from behind the arc in the second. Boston allowed Donovan Mitchell to have another big game with 25 of his 29 points in the second half and still couldn’t stop five of his teammates from reaching double figures.

Brown was still simmering after the game. He sat in front of his locker in his jersey shorts for about 20 minutes before eventually heading for the showers. A man of few words during several recent interviews, he opened up more during his postgame news conference, as if to issue a challenge to his team. Urgency dripped from Brown’s every word as he said the lack of defense upset him the most.

“I think just overall maybe we missed some shots and we let that translate (to other parts of the game),” Brown said. “It’s the playoffs. That can’t happen. I don’t care if you’re missing shots, you’ve gotta guard the guy on the other end.”

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The even-keeled Tatum sounded less pained. When asked about his recent shooting troubles, he said his own scoring is the least of his worries. He said the Celtics need to improve their defensive communication but credited the Cavaliers for making tough looks. He did not like Boston’s offensive spacing but said he believed his team simply missed shots. Given the Celtics’ 8-for-35 showing on 3-point attempts, their second-worst percentage of the regular season and playoffs combined, he probably had a point. As Brown stressed, Boston’s troubles went deeper than that. Tatum still wanted to turn down the volume on all the alarm sure to follow his team.

“The world thinks we’re never supposed to lose; we’re supposed to win every game by 25,” Tatum said. “And it’s just not going to be like that all the time. So we don’t expect it to be easy. It’s a good team we’re playing. It’s the second round of the playoffs. So it’s just going to be fun the rest of this series, especially come Saturday. We’ve bounced back plenty of times. We lost what, 16 games this year? So I’d like to think that we responded pretty well the few times that we did lose.”

Tatum was mistaken about at least one detail. The Celtics lost 18 games during the regular season, not 16. Like he suggested, though, the playoffs carry danger. With very few exceptions, every postseason run involves major setbacks. Not every journey is the same. Not every game is the same. A team can look helpless one night and unstoppable the next. Even most championship runs come with bumps and bruises. The 2008 Celtics, just one such example, didn’t win their first postseason road game until the Eastern Conference finals. They needed seven games to eliminate a 37-win 8-seed in the first round and another seven to defeat a 23-year-old LeBron James and Cleveland’s flawed supporting cast. Sixteen years later, nobody cares how much trouble that Celtics team ran into against a rookie Al Horford because that rocky road led to a Boston championship.

Like then, the pursuit of a title is all that should matter to the Celtics now. The bracket is set up well for them in the Eastern Conference. Joel Embiid has been eliminated. The Knicks, as admirably as they’ve played, are running out of usable players. The Pacers, down 2-0 to New York in their second-round series, have not resembled a contender. The Cavaliers can be formidable, especially when Mitchell is getting teammates involved, but the Celtics remain heavy favorites to win the series even after the Game 2 disappointment.

At home, it was a shocking loss. The Cavaliers entered the game with the 15th-ranked offense out of the 16 playoff qualifiers, but they tore apart Boston’s defense for an eye-opening 128.3 points per 100 possessions. Before the fourth quarter, Brown walked over to his other teammates on the court and appeared to give them each a word of encouragement. Even from afar, the message seemed obvious: It’s time to brush aside the malaise. It’s time to tighten up and take control. The Celtics just couldn’t wake up the way he wanted. They gave up a 13-5 run to begin the fourth quarter. That came after Mitchell ended the third quarter with a contested, stepback 3-pointer to extend Boston’s deficit from nine to 12 points.

“At the end of that third it was kind of like right there,” Horford said. “And Donovan makes a tough shot like Payton (Pritchard) made a tough shot in Game 1. And that happens, but I felt like even though they hit us and we were kind of there, I still felt good going into the fourth quarter. And for a good part of the fourth it was just about trying to get something going and we just weren’t able to.”

The Celtics never surged like they did so many times this season. Now, they need to make sure the loss, as frustrating as parts of it were, will not matter. This type of challenge is why Mazzulla occasionally said throughout the season that he wanted the Celtics to experience difficult times. After one January comeback win against the Pelicans, Mazzulla sounded much like Tatum did Thursday night. Back then, Mazzulla said there’s a sense of entitlement around the Celtics, like people think they should play amazing basketball all the time. That’s just not how the NBA works, Mazzulla said. He said the expectation that a game is supposed to go a certain way all the time can be extremely unhealthy.

Looking back, Mazzulla was preparing the Celtics for moments like this. A series has gone sideways. The pressure has shifted further onto Boston. Talking heads will debate whether the ugly loss shows the Celtics still don’t have what it takes to win a championship. It’s possible they don’t, but only what comes next will decide that.

(Photo: David Butler II / USA Today)