Maria has pulled out of the season-ending WTA Championships in Istanbul after suffering successive straight-sets defeats.

Sharapova lost to China's Li Na 7-6 (7-4) 6-4, who had herself not won a match, or even a set, since August.

It was a match that ebbed and flowed as Li came from 2-4 down in the first set to force a tie-break, which she won despite losing the first four points.

Maria Sharapova's serve let her down again, and this time there wasn't much she could do about it.

The three-time Grand Slam champion had experience on her side Saturday in the Wimbledon final. Petra Kvitova was just plain better, beating the fifth-seeded Russian 6-3, 6-4.

"She was hitting really powerful and hitting winners from all over the court. She made a defensive shot into an offensive one," Sharapova said. "And, yeah, just kind of laid on a lot of those shots. I think she was just more aggressive than I was, hit deeper and harder, and got the advantage in the points."

The most eligible bachelorette in tennis is off the market.

Three-time Grand Slam champion Maria Sharapova got engaged to her boyfriend, Los Angeles Lakers guard Sasha Vujacic, after he proposed on Tuesday night at his Manhattan Beach, Calif. home. The two had been dating for nearly a year. TMZ was the first to report the news. Sharapova's agent has since confirmed it to CNBC's Darren Rovell.

Sharapova and Vujacic first went public with their relationship last November when they were seen cuddling at a U2 concert in Los Angeles. Since then, the relationship has become the fodder of tabloids and paparazzi, as the athletes have been photographed together in Los Angeles and Italy, where they vacationed.

Three-time Grand Slam winner Maria Sharapova has confirmed she will play in the Auckland Classic in January, tournament organisers in New Zealand said.

The Russian former world number one would be a major drawcard for the event as she warms up for the Australian Open Grand Slam later that month, tournament director Richard Palmer said on Wednesday.

"(It) is a major boost to the tournament and to the sport, her popularity is huge," Palmer said.

The 23-year-old, currently ranked 17 in the world, has struggled to come back from a crippling shoulder injury this year that forced her to adjust her explosive serve, failing to reach the second week in all four majors.

At the 2010 CFDA Vogue Fashion party Maria Sharapova confessed that she loves fashion almost as much as she loves tennis. "I thought the show was incredible, and it is so important because it gives notice to designers that are up and coming and gives them exposure. Fashion is so expressive and every designer has their own take and their own appeal."

Sharapova is also a designer and has a fall line with Cole Haan. "I get my inspiration for my own line through traveling," she said. "I love street style. I'm always stopping people on the street and taking pictures of them!"