NEW YORK — Celtics general manager Danny Ainge was fined $25,000 by the NBA on Thursday for tossing a towel to try and distract Cavaliers forward J.J. Hickson as he shot a free throw.

Ainge, who was sitting courtside under the Cavs' basket, flipped a white towel over his head during the third quarter of Monday night's playoff game between Boston and Cleveland. The Celtics led by 23 points at the time, and Hickson made the free throw anyway.

Stu Jackson, the league's executive vice president of basketball operations, fined Ainge for "an unauthorized distraction and for conduct detrimental to the game."

Celtics coach Doc Rivers said after the team's practice in Waltham, Mass., on Thursday that he was surprised Ainge was fined.

"That's a lot of towels. Those are some Grade A towels that Danny bought, for sure," he said with a laugh. "What's the difference between that and mascots, (who) do it all the time. I was wondering if Danny had borrowed (Celtics mascot) Lucky's outfit. He could try that."

Boston went on to win 104-86 to even the Eastern Conference semifinal at 1-1.

On Wednesday, Ainge said he regretted his behavior, calling it "unprofessional."