BOSTON — Kawhi Leonard and Lou Williams have played Jayson Tatum before, but they have never played this Jayson Tatum before.

Even when the Los Angeles Clippers and Boston Celtics met back in November, Tatum wasn’t quite at the level he is now. In the Celtics’ 141-133, double-overtime win against the Clippers on Thursday at TD Garden, there were many moments it felt like Tatum wasn’t just one of Boston’s top players — he was Boston’s star player.

The third-year forward dropped a game-high 39 points, hitting one pivotal bucket after another down the stretch. He spent much of his night being guarded by Leonard, one of the league’s best defenders, and hardly seemed fazed by it.

Suffice to say he has the Clippers’ attention.

“He’s more assertive,” Leonard said. “They’re giving him the ball, trusting him, he trusts in himself. He’s doing his thing.”

“He’s become the clear-cut leader of that basketball team,” Williams added. “He made play after play down the stretch right there and he’s on his way to Chicago, he’s on his way to Chicago for a reason. He’s just leading this group. Very talented, so young and his best years are ahead of him.”

Los Angeles head coach Doc Rivers couldn’t help but joke that he doesn’t want Tatum to have more room to grow because he’s already getting torched by the 21-year-old.

That was before the game.

Afterward, it’s easy to understand why.

Here are some other notes from Celtics-Clippers:

— It really can’t be overstated how impressive it was that Tatum dropped 39 points with Leonard following him most of the night.

By the sound of it though, Tatum has been waiting for this moment for some time.

“I’ve been watching film on him since high school,” Tatum said. “Obviously one of the best players in the league. You want those moments and just to compete against a guy like that who’s accomplished so much in this league.”

This marked the third time over the last five games Tatum has put up at least 30 points, and it’s the eighth time this season he’s reached that mark.

— Also eclipsing 30 points, and for just the second time in his career, was Marcus Smart, who scored 31.

Smart hit half of his 20 field goal attempts, 14 of which were from 3-point territory (he made five of his shots from distance).

The veteran guard has made a concerted effort over the years to become more of a shooting threat from the perimeter, and that work is beginning to pay dividends.

— Things started to get dicey in the second overtime period for the Celtics.

Daniel Theis had fouled out, Enes Kanter’s hip seemed to be bothering him and Grant Williams not only had played poorly all night but had five fouls.

But Williams and Hayward played well defensively through those five minutes, giving the Celtics a cushion they so desperately needed.

“I thought their plays came on defense,” head coach Brad Stevens said of Williams and Hayward. “I thought Gordon was good on Lou at the end. He gives a lot of people fits. Grant made some great plays in traffic there and helped. We were really struggling with the pick-and-rolls with Lou and Kawhi there for quite a bit of the game.

“We went super small and switched a lot and changed up the matchups and we had to check to make sure Grant was still alive after (Montrezl) Harrell dunked all over him. Other than that I thought he did a lot of good things.”

— With the All-Star break now underway, the Celtics are going to have some time off. Tatum and Kemba Walker will be participating in the All-Star festivities in Chicago, but otherwise will have a chance to get away like the rest of their teammates.

The Celtics will return to game action Friday, Feb. 21 against the Minnesota Timberwolves.

Thumbnail photo via Greg M. Cooper/USA TODAY Sports Images