The Associated Press

DALLAS - There are moments that can define not only a game, but an entire playoff series.

Dirk Nowitzki and the Dallas Mavericks can only hope that one of them didn't happen early in the fourth quarter Friday night.

Nowitzki went down with a sprained left knee as Tim Duncan was leading San Antonio on a 12-0 run to open the fourth quarter, and the Spurs controlled the game the rest of the way to beat Dallas 96-83 and take a 2-1 lead in the Western Conference finals.

Duncan scored 14 of his 34 points in a lopsided fourth quarter that sent the fans streaming to the exits with more than 3 minutes left. Duncan had 24 rebounds, and Tony Parker scored 29 points for the Spurs.

Coach-general manager Don Nelson said Nowitzki will undergo an MRI today, but he's not optimistic about what it will show. Game 4 is Sunday night in Dallas.

"The news is not good," Nelson said. "His knee is very sore. I don't expect he'll play, and I'm not sure if he'll play in this series. We should not take a gamble or a chance on Dirk Nowitzki. I told Dirk he must feel he's totally 100 percent for me to play him again this series."

It was a stunningly quick turn of events.

Dallas had a few good moments - mostly in the second quarter - before Nowitzki banged his left knee against Manu Ginobili of the Spurs while going for a rebound.

Nowitzki stayed down for about two minutes before being helped off the floor, unable to put any weight on his leg.

"I didn't see anything," Ginobili said. "I was surprised when we came back that he was still there. I didn't mean to hurt him."

The last time there was such a scene, it was Chris Webber of Sacramento being carried off the court in Dallas during Game 2 of the second round. He never returned to the series.

ROCKETS: Rudy Tomjanovich stepped down as coach to take another job with Houston after 12 seasons that included the franchise's only two NBA championships.

Tomjanovich, who cut short his season for treatment of bladder cancer, said he looked forward to resuming a more normal lifestyle.

"Just to be one of the people in this city, being a soldier instead of a general for a while, I look forward to that," Tomjanovich said, choking back tears.

Tomjanovich led the Rockets to the NBA title in 1994 and 1995, but the team hadn't made the playoffs the past four seasons.

NETS-PISTONS: The Nets can make it 10 playoff wins in a row tonight when they try to complete a sweep of the Detroit Pistons in the Eastern Conference finals.

CAVALIERS: Jeff Van Gundy and Paul Silas remain the leading candidates to become the team's coach, general manager Jim Paxson said.