When the Celtics (and Jason Tatum) needed it, Jalen Brown stepped up. I saw what happened after that.

How?

The answers to how the Celtics made an incredible shift in momentum and thrilling victory in their first Final since 2010 are plentiful.

They will require an extraordinary effort salute in the fourth quarter, among others, Al Horford (11 of his 26 points), Derek White (two of his five three-pointers and six of his 21 points), and, in one sense, Tatum, who distributed four of his 13 assists. decisive in a performance in which he never hesitates to try to deliver the right play).

But there was one player who, through spirited and aggressive play at the start of Match 4, ignited a match that turned into a hell of a comeback. He told us who he was, Mr. Horford:

“I think the key for us was Jalen Brown,” Horford said from the podium. “[At the] The start of the fourth quarter, the way he looked and played, his card and scoring, but then also Rob Williams got a big hit. [off a Brown pass]. I just think that was the start for us of something out there.”

It was the start of something special and something we will remember for a long time if the Celtics win this series. And it came at a time when it was reasonable to question whether the Celtics were finished, at least for tonight.

The Celtics took a 54-52 lead at the end of the first half, having topped 21 first-quarter points from Steve Curry. But the Warriors came out on fire in the third quarter, outplaying the Celtics 38-24 and taking a 12-point lead to fourth.

If at that point your thoughts turned to Game 2 and what the Celtics had to do to salvage a win at Chase Center before the series moved to Boston, you can’t be blamed. Warriors can make you feel like they are inevitable.

But Brown, who shot 66.7 percent from the field in the fourth quarter during these playoffs, was certainly not thinking that way.

We knew they would come out [aggressive] In the third quarter, they did. They came out great.” “In those moments, once you realize that you let someone do something you didn’t want, once you realize that, you can either go two ways: you can let them snowball or you can play in the next play, personal things out.” .”

After shooting 6 of 17 during the first three quarters, he not only figured things out — he took charge.

Near the 11 minute mark, he hit a jump over Draymond Green. (Warriors Still Lead, 92-82). Then, a 3-pointer in Jordan Paul’s face, he made his first in six attempts to that point from behind the bar (92-85). After Paul’s turn, Brown established Robert Williams III for a resounding dip (92-87).

Warriors coach Steve Kerr called for the timeout, but that didn’t solve anything. Brown picked up a stray pass from Andre Iguodala from the sky and found Payton Pritchard to quickly throw the ball (92-89). Iguodala finished the Celtics 9-0 with a header, but Brown followed with a 3 (94-92) corner hole.

The Celtics didn’t take the lead and lead the game forever until two minutes later, when Horford hit 3 consecutive throws to give the Celtics a 109-103 lead in what would be 17-0. But Brown helped mark the victory with a neat platter of Horford’s traditional 3-point play with 48.3 seconds left.

Hurford bowed before the Chase Center crowd, maybe 10 percent of whom could tell you who Nate Thurmond was, after what would be the Celtics’ last basket of the night. But it was Brown who did the heavy lifting at the start of the quarter to make it all possible.

There’s no denying Jaylen Brown vs Draymond Green in the second half.Ezra Shaw/Getty Images

Brown finished with 24 points – second to the Celtics to Horford’s 26 – in 38 minutes of playing time. Ten of his points came fourth, as did all of his five passes. This second stat is particularly impressive considering that Brown’s gaming instincts sometimes betray him when he’s happy to dribble.

It’s something he grows and learns about,” Celtics coach Im Odoka said.[He’s] He is still learning to play in this crowd and make the correct reading on occasion. At the start of the match… he had some twists and some big shots. We showed that in the first half we don’t have to take any of those.

“[He] It was a great start to the fourth quarter. With JT struggling a bit, we went for it more. He was very aggressive during his descent. I got the seniors against him and he got the shots he wanted.”

Brown got the shots he wanted, and helped get the shots his teammates wanted too. Before warriors knew it, they were cast upon Celtic after making Celtic, a type of scoring attack they would usually offer rather than endure.

How Did the Celtics do it?

Simple: They followed Jaylen Brown’s lead as the deficit turned into a comeback, then a very satisfying victory.

Read more Celtics stories

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Celtics make their way again, and other notes of a stunning win | instant analysis

Dan Shauncey: Celtics comeback capped championship caliber, and that was everything an NBA Finals game should be

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HOW IT HAPPENED: The Celtics staged a furious crowd rally in the fourth quarter to defeat the Warriors, 120-108


Chad Finn can be reached at chad.finn@globe.com. Follow him on Twitter Tweet embed.