By A.Sherrod Blakely
CSNNE.com
SAN ANTONIOOne big man returns, another one leaves.
Seems like it's been that way for the Boston Celtics all season.
It certainly was on Thursday, with the return of Jermaine O'Neal coinciding with a right knee injury to starting center Nenad Krstic that will keep him out for at least the next two games.
Coach Doc Rivers said Krstic will undergo an MRI to determine the extent of his injury.
If Krstic's injury is as serious as it looked in the second quarter of Boston's 107-97 win at San Antonio, it wouldn't be the first time he has suffered a significant knee injury.
While with the New Jersey Nets -- then coached by current Celtics assistant Lawrence Frank -- Krstic suffered a torn ACL injury to his left knee that sidelined him for the entire season.
Boston Celtics
Now that the Celtics are without Krstic, they once again find themselves short-handed at the center position.
In fact, the only true center they have now is Jermaine O'Neal, who returned to action on Thursday for the first time since Jan. 10 -- a span of 36 games.
The return of Shaquille O'Neal to the Celtics is up in the air.
Danny Ainge, Boston's president of basketball operations, told WEEI that O'Neal would be back Sunday or Tuesday of next week. Meanwhile, Rivers said he isn't sure when O'Neal will return, adding that his longer-than-expected time recovering from a series of right leg injuries may "bleed into" the playoffs.
"I just don't know because I've never had this situation," Rivers said of Shaq's return. "It's getting to become a challenge. It wasn't before, because I just viewed it as a regular season injury. Now it's starting to get close to bleeding into playoffs. Now that becomes a challenge."
When you add the uncertainty that exists now with Krstic's injury, the Celtics' frontline may have yet another hurdle to overcome between now and the postseason.
A. Sherrod Blakely can be reached atsblakely@comcastsportsnet.com.Follow Sherrod on Twitter at http:twitter.comsherrodbcsn