Ninety minutes before tipoff Thursday night at TD Garden, someone asked Clippers Coach Doc Rivers if Jayson Tatum has grown as a basketball player in the 12 weeks since he coached against him in Los Angeles.

“I hope not because he was pretty good against us that night,” Rivers said. “I don’t need any more growth out of him right now.”

It was a false hope, and the former Boston Celtics coach knew it. Tatum showed Doc and an enthralled, packed house how rapidly he’s blossoming during a thrilling 141-133, double-overtime victory over the Clippers in front of a wild crowd that never lost its intensity.

Tatum scored 30 points 12 weeks ago at Staples Center, where the Clippers prevailed, 107-104, in overtime.

He outdid himself in the rematch, totaling 39 points and nine rebounds in 48 minutes, outplaying Kawhi Leonard, MVP of the NBA finals last season for the Raptors, on a night fellow young Celtics star Jaylen Brown did not play.

“That was an extremely fun game to play in,” Tatum said.

And to watch.

Tatum, who turns 22 on March 3, could not have done a better job of proving himself worthy of his first All-Star selection. Not the most excitable player in the NBA, Tatum showed more emotion than usual Thursday, especially after scoring on a late drive over shot-blocking beast Montrezl Harrell.

“I did get a little excited,” Tatum said when asked about the fire in his eyes after that big bucket. “I try to be as calm as I can and try to keep a poker face and just move onto the next play, but basketball is a game of emotions and the crowd was into it and I got excited a little bit. I try to stay calm.”

Don’t try too hard. The crowd loved the fiery display as much as the bucket itself.

The emotions went back into hiding by the time Tatum met the press well after the game. He conducted himself in a way to make it obvious he’s mindful of not getting too high on himself. Tatum made sure to point out repeatedly that defending Leonard was a group effort and the question about matching up against the superstar had to be asked twice before he addressed it.

“It’s definitely a challenge. He’s a guy I’ve watched film of a lot,” Tatum said. “I have been watching film of him since high school. He’s one of the best players in the league, probably top two, three players in the league. You want those moments, just to compete against a guy like that who has accomplished so much in this league. You just try to make it tough. He’s capable of making any shot he can get. It’s a team effort. You just try to make it as tough as possible, and that’s what we did.”

On a night Tatum scored 39 points, an argument could be made that he played even better defensively.

Tatum made 14 of 23 shots and 5 of 10 3-pointers. To get his 28 points, Leonard took 27 shots, made 10, and hit just 1 of 6 3-pointers. He added 11 rebounds and four assists.

“I’m just happy we won,” Tatum said, skirting another question about the job he did defensively on Leonard. “That would have been tough playing that hard as a team and not coming out with a victory. It’s a team effort, guarding those guys, especially a guy like Kawhi. You just show him bodies, contest, hope he misses.”

Tatum went hard to the basket and had to weave through explosive athletes with big bodies. When he got past Leonard, Harrell often was waiting. Tatum didn’t retreat. He advanced. He finished. He dominated.

“Basketball is based off of instincts, reading the game, being able to make quick decisions in tight spaces,” Tatum said. “I’m just trying to do the best I can.”

He made those quick decisions in tight spaces efficiently, magnificently, against the Clippers. He’s doing it better all the time, no surprise considering that this is just his third NBA season after one year at Duke.

Rivers shared his thoughts before the game on what has enabled Tatum’s improvement.

“He’s just taking better shots. Shot quality is better than it was last year,” Rivers said. “He seems more confident, free in a positive way. It’s just another year. He’s so young still. I think we really forget that. He’s 21. … Jayson, can you imagine five years from now what he’ll be? I mean he’s one of the better players in the league. He’s an All-Star, yet we’re still talking about how young and how much better he’ll be. He’s going to be amazing. I’m glad he’s in the East.”

Tatum has topped the 30-point mark three times in his past five games, has done it eight times on the season, and is averaging 29 points in the past five games. His 22.4 scoring average leads the Celtics, just ahead of fellow All-Star Kemba Walker (21.8).

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