Jayson Tatum Apologizes To Janet Jackson For Forcing Concert Postponement

The Celtics' closeout win over the Hawks on Thursday was apparently bittersweet for Jayson Tatum ... who admitted after the game he was kinda pissed it ultimately forced Janet Jackson to postpone one of her concerts.

Just after Boston took down Trae Young's squad in Game 6 of the Celts' playoff series with Atlanta, Tatum got on the courtside microphone ... and said he was sorry to Jackson.

If you're unfamiliar, because Boston didn't beat the Hawks in Game 5 ... the two teams had to return to State Farm Arena on the same night Jackson was supposed to perform as part of her "Together Again" tour. The decision was made to move her show to Friday night so the NBA playoff game could be played.

Tatum was clearly bothered by it all ... because after he helped the C's to a 128-120 win -- he told NBA on TNT, "I want to say an apology to the legend Janet Jackson."

"We were supposed to close out in Boston and she had to postpone her show. I hope she sees this. I apologize for that."

No word yet from Jackson on the matter ... but we're sure she appreciates the shoutout nonetheless.

As for where Tatum goes from here ... Boston's next series against the Sixers will begin on Monday -- leaving him plenty of time to potentially catch one of Jackson's three shows this weekend.