Dinara Safina pulled out of the Sony Ericsson Championships at Doha, Qatar after just two games with a serious back injury yesterday, handing the year-end No. 1 ranking to Serena Williams.

Safina said a disk in her lower back was "starting to fracture" and the injury has been bothering her for three months. She said doctors told her she will be sidelined for at least six weeks, and that she may not be fit in time for next year's Australian Open.

"I went yesterday to have injections, cortisone," she said. "But I just couldn't handle this pain."

Safina, the main No. 1 since April, regained the top ranking this week, but her margin over Williams was so slim that the player who performed best in Doha was guaranteed to end the year as No. 1.

Williams won her first match on Tuesday and beat sister Venus, 5-7, 6-4, 7-6 (4), yesterday.

"It's such a great feeling," Williams said about being back at No. 1. "Dinara is such a great player. She must be really hurt, because she never gives up."

Safina was replaced in the White Group by compatriot and first alternate Vera Zvonareva, last year's runner-up to Venus Williams.

Doha is the season-ending tournament for the top eight players in the world.

GOLF

WHAN TO LEAD LPGA

The LPGA Tour picked Michael Whan as its new commissioner, turning to a former marketing executive in golf and hockey equipment to rebuild the tour's relationships with sponsors.

The 44-year-old Whan previously worked for TaylorMade Golf and Wilson Sporting Goods and most recently was president of Mission-Itech Hockey.

"I was that crazy high school kid cutting greens at 5:30 in the morning so he could play free golf in the afternoon and caddying on Sundays," Whan said yesterday, during an introductory news conference at Madison Square Garden.

He replaces Carolyn Bivens, who was forced out by players in July as the tour kept losing sponsors. Bivens had a strong business background but little experience in sports when she was hired in 2005.

SWIMMING

U.S. AGAINST EUROPE

Michael Phelps will lead the U.S. team at Duel in the Pool against a squad of European swimmers.

USA Swimming announced a 36-person team yesterday. The roster includes 17 Olympians, including Phelps, who broke Mark Spitz's Olympic record by winning eight gold medals at the Beijing Games.

Olympic gold medalists Ryan Lochte, Aaron Peirsol and Rebecca Soni also were selected to face a group of top swimmers from Britain, Germany and Italy.

Duel in the Pool, sponsored by Mutual of Omaha, will be held Dec. 18-19 in Manchester, England.

AND WHAT'S MORE ...

Harness racing driver Jeff Gregory, a 25-year veteran, earned his 6,000th career win yesterday when he drove Montana Steel to victory in the third race at Freehold Raceway in Freehold, N.J. ... Tom Lehman has withdrawn from the Charles Schwab Cup Championship in Sonoma, Calif., because of an undisclosed family emergency, leaving 29 players in the season finale on the Champions Tour.