Knicks guard RJ Barrett runs downcourt against the Clippers in...

Knicks guard RJ Barrett runs downcourt against the Clippers in the first half of an NBA game at Madison Square Garden on Monday. Credit: Kathleen Malone-Van Dyke

WASHINGTON — RJ Barrett walked into Capital One Arena smiling and laughing, went through an on-court workout and hit the weight room. Barrett was listed as a game-time decision, but coach Tom Thibodeau said he looked much better Friday night after missing the previous two games with a migraine.

But a half-hour before game time, the Knicks announced that Barrett would be sidelined for a third straight game with the migraine. He joined Quentin Grimes in street clothes; Grimes was ruled out with a left wrist sprain suffered in the fourth quarter of Wednesday night’s win over Atlanta.

The Barrett decision was more surprising, as he seemed to be showing no ill effects of the migraine, even joking with media members (while not taking questions) in the locker room before the game. Thibodeau said Barrett had been on the court this week, although the team canceled Thursday’s practice and Friday morning’s shootaround. And he spent the game on the bench despite the bright lights and loud music.

“Look, he was very sick,” Thibodeau said. “That’s all I’ll say. And if he’s not ready, he’s not ready. You trust the medical people, you trust him and you go from there. He warmed up. He said he wasn’t quite there. We’ll see where he is tomorrow, but each day has been a lot better.”

Barrett was called a game-time decision earlier in the day and seemed to be himself as he worked out. Thibodeau said the decision to remain sidelined was Barrett’s.

“Just probably getting back and getting his wind,” Thibodeau said. “He’s still, he’s feeling fatigued. So there’s stuff you normally feel when you’re sick. When he’s ready to go, he’s ready to go. I don’t know if they were able to find out specifically what it was, but he was very sick.

“You know, we trust him. He worked out this morning, he worked out before the game. If he says he’s ready to go, then he goes. If he’s not ready, then the next guy, get in there and get the job done.”

Thibodeau spoke of Grimes as a day-to-day proposition, but his left wrist was encased in a soft black cast. With another game in Charlotte less than 24 hours after this game, it is hard to imagine that he will be back.

“It’s just a sprain,” Thibodeau said. “So we’ll see where he is [Saturday].”

With the two wings out of the starting lineup, Thibodeau started Josh Hart and Donte DiVincenzo alongside Jalen Brunson, Julius Randle and Mitchell Robinson. Hart started the previous two games in place of Barrett, but this marked DiVincenzo’s first start with the Knicks.

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