Krstic is listed as day to day and the team said he simply has a bone bruise.
Krstic's knee bent awkwardly as he ran through the paint on offense late in the first half of Thursday's win in San Antonio. He grimaced before collapsing beneath the basket and clutching the knee in pain. He eventually got to his feet and hobbled to the locker room with the aid of team trainer Ed Lacerte.
The 7-foot center, who started his first 18 games with Boston after being acquired from Oklahoma City in the Kendrick Perkins deal, sat out Friday's game against the Atlanta Hawks and coach Doc Rivers previously said he was unlikely to play in Sunday's visit from the Detroit Pistons.
But the team's diagnosis suggests that Krstic could be back as early as Tuesday's tilt with the Philadelphia 76ers. Boston got a boost at the center spot on Thursday when Jermaine O'Neal (left knee surgery) returned for the first time since Jan. 12 and the team is still hoping center Shaquille O'Neal, sidelined since Feb. 1 due to right foot injuries, could be back as early as Sunday as well.
Krstic tore his left ACL as a member of the New Jersey Nets in December of 2006 and missed the remainder of the season. In 18 games with Boston this season he's averaging 9.3 points and 5.6 rebounds over 24.3 minutes per game.
Celtics captain Paul Pierce said after Thursday's game that he hoped the injury wasn't too serious and that getting everyone healthy before the postseason was the goal.
"Hopefully Krstic is not too hurt and he'll be back in a few days or a week or however long he takes," said Pierce. "But we want to be healthy going into the playoffs, bottom line."
Chris Forsberg covers the Celtics for ESPNBoston.com.