The Celtics got one impact big man back on Thursday night, with the return of Jermaine O'Neal, but they lost another. Nenad Krstic has injured his right knee and is out for the foreseeable future.

"Nenad, I don't know," coach Doc Rivers said after Thursday's game, a 107-97 win over the Spurs. "He's out obviously this weekend. MRI. That's as far as I'm going to go."

Krstic left with 2:18 left in the first half of Thursday's game. He was leaping into the paint when he landed awkwardly on his right leg. His knee became bent out of shape and he immediately felt the pain. Krstic limped off the floor with the help of Celtics trainer Ed Lacerte.

While the rest of the Celtics head straight to Atlanta, where they close out their four-game road trip on Friday night against the Hawks, Krstic will return home to Boston. He will undergo an MRI on Friday.

Krstic has played 18 games for the Celtics since being traded from Oklahoma City to Boston on Feb. 24, starting all of them. He's averaged 9.3 points and 5.6 rebounds per game.