While he briefly appeared after halftime, he went back to the locker room, and the Celtics announced he was questionable to return to the game thanks to a non-COVID illness. He did not return and the Knicks overcame a 20-point deficit to win 118-115 in overtime.

BOSTON (AP) — Celtics center Kristaps Porzingis didn’t play in the second half of Boston’s 108-105 overtime loss to the New York Knicks in Game 1 of the Eastern Conference semifinals because of an illness. Porzingis wasn’t on the floor initially with the team Monday night as they warmed up prior to the start of the second half.

After the game, Celtics head coach Joe Mazzulla was asked about Porzingis' status. "Yeah, I haven't seen him yet. We'll check on him. But, I mean, obviously it impacts the game wi