Jayson Tatum helps Celtics survive to take 3-0 series lead over Pacers. Did Boston prove its championship mettle?

INDIANAPOLIS — Jayson Tatum’s favorite postseason matchups are Game 3s. “Going into an opponent’s home building, it’s their first home game, the crowd is electric,” Tatum said. He’s accustomed, mind you, to the third battle of a series taking place on the road, as Boston has earned home-court advantage in at least the first round of the playoffs during six of Tatum’s seven seasons with the Celtics, including a top-two seed in each of the past three years. He dribbles with aggression and defends with intensity and rounds his massive shoulders for critical plays on the glass. He senses a moment and the requirement to deliver.

Tatum viewed Gainbridge Fieldhouse as a hostile environment he needed to silence Saturday night. The Pacers had not lost in this arena, in front of this golden sea of checkered-flag T-shirts, since March 18 — including a 6-0 postseason slate. Indiana seemed well on its way to extending that streak, even without injured All-Star point guard Tyrese Haliburton, thanks to a blistering mid-range shooting display that built an 18-point lead as late as 6:04 in the third quarter.

Lineup tweaks and matchup adjustments from Celtics head coach Joe Mazzulla helped Boston inch and inch its way into another crunchtime contest. And who was it but Tatum, finishing with 36 points, 10 rebounds plus 8 assists — the first in NBA postseason history to tally those numbers without a single turnover — drawing two on a powerful drive with just over a minute remaining. Tatum saw Myles Turner had sagged down the baseline and read the Pacers center like a children’s book. If he was here, that meant Turner left his actual assignment, the Celtics’ ageless big man, Al Horford. And once Tatum convinced Turner, plus two other defenders, that he was launching in the lane, Tatum sent his dribble behind his back, the ball bouncing once and directly into Horford’s shooting pocket.

“I trusted that he was gonna be there,” Tatum said, and Hoford’s seventh triple of the contest — five of which were assisted by Tatum — splashed through cotton. It’s the type of playmaking brilliance that earned Tatum first-team All-NBA honors this week for the fourth straight season. It was the type of postseason pass that will sizzle on highlight reels well beyond when this Celtics’ run stops cooking, something that deserves commemoration. “Hang it in the f**king Louvre,” said Jaylen Brown, the Celtics’ All-Star wing.

Boston, of course, only really cares about hanging banners, and this gutty 114-111 victory, claiming a 3-0 series edge over Indiana, may be the Celtics’ greatest claim yet the league’s best regular-season team can truly withstand this playoff gauntlet. Yes, injuries have riddled each of Boston’s postseason opponents — Haliburton's hamstring follows Donovan Mitchell’s calf and Jarrett Allen’s ribs and Jimmy Butler’s knee and so on — but this early struggle against the Pacers felt terribly reminiscent of the Celtics’ Game 2 losses in each of their first two series, like the jarring instances when Boston’s high-powered offense looks anything like the sort, until this time — Boston withstood.

The Celtics' defensive execution lacked timing and tenacity. Outside of Tatum and Horford, the Celtics’ other shooters clanked shots, connecting on just 4-of-22 from distance. “When those things don’t happen for us in the past,” Horford said, “it hasn’t been good.” Mazzulla, though, has been preparing Boston for this game’s particular challenge, for any game’s particular challenge, all season. “Joe always talks about, ‘It’s not always gonna go how we want it to, or we expect it to,’” Tatum said. These 48 minutes rarely go to script, but Mazzulla preaches being ready to scribble over everything with red ink.

“Joe was trying to do anything and everything that he could to kinda get us going,” Horford said.

“At one point, I looked at the scoreboard and I was like, ‘Dallas was down 18 last night,” said Mazzulla, referencing the Mavericks’ own comeback to steal a 2-0 series lead over Minnesota in the Western Conference finals. “This has to be normal. We have to know that we’re going to be losing in the playoffs and we have to play through it.”

Mazzulla and All-Star point guard Jrue Holiday have spent all season whispering across the sideline about how to change some coverage here, invert some action there, to regularly disrupt their opponent. Holiday’s rare ability at just 6-foot-4 to guard all five positions unlocks almost any lineup or adjustment Mazzulla can imagine, like sticking the point guard onto Turner — even after a fever left Holiday bedridden with chills all day with his status undetermined until warmups. And so Boston showed Indiana plenty of zone before switching to man-to-man with reserve center Xavier Tillman.

“We’ve switched up so many times and done so many different things against everybody in the league that we really feel like we can do a lot of different defensive stuff,” Holiday said.

Holiday’s exclamation point of the evening came on that side of the floor, a vintage pickpocket in transition, but that came only after the veteran guard, the only Celtics player to hold a championship ring, lowered his shoulder into Pascal Siakam and delivered the go-ahead three-point play with 39 seconds left. Then, after Tatum’s last and final drive missed wide, Holiday swarmed Pacers guard Aaron Nembhard as he brought the rebound over the timeline. He absorbed a shoulder from Nembhard, who led Indiana with 32 points, and Holiday even needed to touch the wood in order to maintain balance. But he’d beaten the sophomore guard to the spot, stuck his chest in front of the kid’s chest, and poked the ball free.

“That’s a trademark steal that he always gets with the inside hand,” Mazzulla said. “He gets that a lot usually when the guy’s coming down the sideline in transition. I’ve been looking forward to a couple of those. He hasn’t gotten as many as I would have liked this year. It was a big-time play.”

There’s just something about Game 3s. And that same pattern, a third outing being Tatum’s first of the series on the road, waits before Boston in the NBA Finals. The Celtics are just one win short of reaching the championship round for the second time in three years. And yet, these Celtics know exactly what needs to be taken care of on Monday. A year ago, they won three straight after falling into this exact hole against Miami.

“We know for one second we can’t relax,” Tatum said.