Injured Sharapova pulls out Dane Wozniacki will now finish 2011 as world number one

Maria Sharapova has pulled out of the WTA Tour Championships after suffering a second straight defeat at the season-ending tournament.

The Russian was beaten by China's Na Li 7-6 (7-4) 6-4 in her second White Group match to leave her with little hope of qualifying for the semi-finals.
Afterwards it was announced that she was withdrawing from the rest of the event due to an ankle injury that has troubled her in recent weeks.
"The ankle didn't recover as well as I had hoped after my first match," she said. "It limits my movement a lot and it's not something I really want to risk.
"I tried to push it as much as I could but I think it was a little too soon."
The 24-year-old had led 4-1 at one stage in the opening set and then also took the first four points in the tie break, only to then subside in a hurry.
Li surged 5-2 ahead in the second before she suffered an attack of the jitters, losing the next two games to leave her just one clear.

Composure

The French Open champion then slipped 15-40 behind in her next service game before regaining her composure, claiming victory at the first attempt when her opponent hammered a backhand return far too long.
Sharapova's early exit means that Caroline Wozniacki is now certain to finish 2011 as world number one.
However, the Dane was unable to celebrate with a victory in her match, going down 6-2 4-6 6-3 against Vera Zvonareva to leave the Red Group wide open.
Samantha Stosur, who had beaten Sharapova on the opening day of action in Istanbul, also lost on Wednesday.
The Australian was simply unable to hit the same heights as she had managed 24 hours earlier, going down 6-2 6-2 to Victoria Azarenka.
However, the reigning US Open champion could still qualify for the knockout stages, provided she gets the better of fellow grand slam winner Li in her last round-robin match.
"It was a quick turnaround, but I felt like I was ready to go," said Stosur afterwards. "It just wasn't fast or crisp enough. I felt like I got pushed around the court."
Azarenka, the fourth seed, broke four times to win in one hour and 18 minutes and take her career head-to-head record against Stosur to 5-0. She next faces Wozniacki in a crucial match for both players, on Thursday.