Paul Pierce  and Kevin Garnett  also eclipsed 20 points and Glen Davis  netted 16 points off the bench for the Celtics (52-22). While Jermaine O’Neal  returned after nearly three months to score five points in 11 minutes, Celtics starting center Nenad Krstic  left the game with a “right knee injury” and did not return.
WHAT WENT RIGHT
Pierce and Rondo asserting themselves: Pierce scored 12 first-quarter points to keep the Celtics competitive despite allowing 33 first-quarter points, and Rondo sparked a 14-3 run to close the third quarter as the C’s established a 77-70 lead entering the fourth quarter. In all, Pierce and Rondo took 36 shots, making 19 of them. Rondo was so good, even his jump shots were falling, causing the Spurs coaching staff to toss their hands up in disgust.
Buckling down on defense: After the Spurs made 12-of-24 shots and scored 33 points in the first quarter, the Celtics held them to 15-of-44 shooting and 37 points over the next two quarters. Entering the game as the league’s sixth-leading scoring team, the Spurs controlled the (quick) pace in the early going, but the Celtics put a stop to that in the second quarter.
The return of Jermaine O’Neal: In limited action, O’Neal played with surprising energy and range of movement, considering he hadn’t seen the court since Jan. 10. He knocked down his only two shots, including an impressive turnaround over Matt Bonner in the first quarter. Should Krstic’s injury be severe, the Celtics will be relying more heavily on O’Neal than they ever expected, and Thursday night’s performance was a positive sign.
WHAT WENT WRONG
Celtics’ bigs problem gets bigger: Just as Jermaine O’Neal got back into the fold, and as Shaquille O’Neal  gets closer and closer to his return, Krstic’s leg bent the wrong way in the second quarter. He left the game clutching his right knee. Krstic did not return, and Celtics coach Doc Rivers  told TNT sideline reporter David Aldridge, “We don’t know for sure, but it does not look good.” In 2006, Krstic tore his left ACL.
Defending the paint: The Celtics gave up 26 points in the paint in the first half and 50 total. Spurs point guard Tony Parker got to the rim at will early, leading all scorers with 14 points in the opening 24 minutes. His ability to penetrate opened things up for the Spurs inside. Of course, Garnett’s two quick first-quarter fouls left the Celtics without their best interior defender in that span for more minutes than they would have liked.
Second-chance opportunities: The Celtics shot 48 percent in the first half, and the Spurs made just 40 percent of their attempts, yet the two teams were tied at the half. The C’s allowed eight offensive rebounds and 15 second-chance points in the first half alone.