Top contenders for WTA Player of the Year

Petra Kvitova (left) and Li Na had Grand Slam breakthroughs in 2011. (AP; Xinhua/Landov)

As the season winds down, it's a good time to take stock of the wide-open but always-entertaining WTA Tour and its race for Player of the Year.

Kim Clijsters began the year by winning the Australian Open for her second consecutive Grand Slam title, and with Serena Williams sidelined by injury, the Belgian looked like she might be the one to separate herself from the pack. But injuries soon derailed her and led to absences at Wimbledon and the U.S. Open and only one tournament appearance since mid-June.

With Clijsters out, a bit of a free-for-all ensued, most notably with the major breakthroughs of Li Na (at the French Open) and Petra Kvitova (at Wimbledon). Then, just when it seemed that the Tour was about to change its motto from "Strong Is Beautiful" to "Let Chaos Reign," Williams re-emerged on the summer hardcourts and appeared poised to restore order by collecting her 14th Grand Slam title at the U.S. Open. Of course, Serena lost her cool and was beaten by a quiet veteran, Samantha Stosur, who played the match of her life in the final.

With the Grand Slams belonging to four different players and injuries and/or inconsistency plaguing many of the top women, the Player of the Year award remains up for grabs and could come down to the WTA Championships next month in Istanbul. Here's how I rank the top candidates right now:

1. Petra Kvitova

Grand Slam Title: Wimbledon

Other Titles: 3 (Brisbane, Paris, Madrid)

Rankings: No. 6 in world; No. 4 in Race

Record: 45-11 (.804)

The 21-year-old Czech leads the list because for six months she was as close as we got to a dominant player. She won Brisbane to open her season; dropped Stosur in the third round of the Australian Open en route to the quarterfinals; beat Clijsters to win Paris; won Madrid with victories against Vera Zvonareva, Li and Victoria Azarenka; and made the Round of 16 at Roland Garros, losing to eventual champion Li.

As if winning three Premier titles on three different surfaces wasn't enough, Kvitova punctuated her rise with the Wimbledon title, knocking off Azarenka in the semifinals and Maria Sharapova in the finals. She became the youngest player to win a Slam since 20-year-old Ana Ivanovic at Roland Garros in 2008.

Of course, after Kvitova hoisted the Venus Rosewater Dish in July, her momentum stalled -- not a stunning development as she dealt with the expectations and scrutiny that come with winning a first Grand Slam event. She arrived on the U.S. hardcourts out of shape and struggled to find her timing, winning two of five matches since Wimbledon and falling in the first round at the U.S. Open. And there's no denying that she's been streaky throughout the year, suffering some shocking defeats, including a first-round loss at an ITF Challenger in Nassau in March.

But even with her two-month slump and inconsistency, she's second only to Caroline Wozniacki in winning percentage this year (excluding Williams, who has played only six tournaments). If Kvitova can rebound and build on her 45-11 record the rest of the year, she'll be tough to beat for the award.

2. Li Na

Grand Slam Title: French Open

Other Titles: 1 (Sydney)

Rankings: No. 5 in world; No. 3 in Race

Record: 31-14 (.689)

Considering her post-Roland Garros drop-off -- which, to be fair, was really a post-Wimbledon slide -- it's easy to forget how strong a year Li has had. At the All England Club, she was the unlucky seed who drew Sabine Lisicki in the second round and played a very high-quality match before losing 8-6 in the third set. With a title and a final to her credit, Li has a case for being the top Slam performer in 2011 -- and that's with the early exit at Wimbledon and a first-round loss at the U.S. Open.

Much like Kvitova, she had a breakthrough first half of the year, upsetting Clijsters for the Sydney title and nearly doing it again in the Australian Open final (which Li reached by rallying past Wozniacki in the semifinals).

Li then had a four-tournament winless streak before bouncing back -- on clay, her least favorite surface -- with semifinal showings in Madrid and Rome ahead of the French Open, where she became China's first Grand Slam champion.

Li has been streaky, for sure, and if the 29-year-old fails to put together a strong fall, the first six months of this year will seem like more of a fluke than they should be. She'll have a great opportunity to re-establish herself in two weeks at the China Open, though it remains to be seen how well she handles the pressure of playing on home soil.

3. Maria Sharapova

Grand Slam Title: None

Other Titles: 2 (Rome, Cincinnati)

Rankings: No. 2 in world; No. 2 in Race

Record: 41-11 (.788)

It would be easy to chalk up her year as disappointing. She had two prime chances to win her first major title since 2008 but couldn't come up with the goods against Li in the French Open semifinals and faced a good player having a better day in Kvitova at the Wimbledon final. We all know that the Slams are the goal for the three-time major winner, so to come so close without finishing weighs heavily in the disappointment column.

But this has been Sharapova's best year by far since her comeback, with two deep Slam runs and significant titles in Rome and Cincinnati. The fact that she's been so close to accomplishing more makes her losses seem that much more devastating, particularly the back-to-back lopsided defeats to Wozniacki and Azarenka in the Indian Wells semifinal and Miami final, respectively. But, again, the numbers bear out a successful year. She's risen to No. 2 in the world and is within striking distance of the top spot in the Race despite having played seven fewer events than Wozniacki.

4. Caroline Wozniacki

Grand Slam Title: None

Other Titles: 6 (Dubai, Indian Wells, Charleston, Brussels, Copenhagen, New Haven)

Rankings: No. 1 in world; No. 1 in Race

Record: 58-13 (.817)

Sure, the closest Wozniacki came to getting her hands on a major title was dating U.S. Open golf champion Rory McIlroy, but you can't fault her consistency throughout the year. She plays a lot and she wins a lot, and while she fell off a bit after Rome (the Dane still picked up a couple of lower-level titles amid the struggles), she rebounded late in the summer hardcourt season, winning New Haven and making her second Slam semifinal of the year in New York.

Yes, there are obvious weaknesses in her game, most glaringly a lack of weapons that seemingly leaves her vulnerable on any given day. But the thing is, she actually doesn't lose often and when she does it generally takes a superlative performance from her opponent.

Consistency may not be the all-important factor when determining the top players on Tour, but it does matter. Don't be surprised if she takes advantage of an exhausted and depleted WTA field and wins the title in Turkey.

5. Samantha Stosur

Grand Slam Title: U.S. Open

Other Titles: None

Rankings: No. 7 in world; No. 6 in Race

Record: 38-18 (.679)

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While the other two Slam winners on this list distinguished themselves in the first half of the year, Stosur was slow off the mark. Anytime she seemed to gain momentum, it was quickly snuffed out. She advanced to the semifinals in Stuttgart and finals in Rome, only to lose in the third round of Roland Garros. Similarly, she made a surprising run to the semifinals of Eastbourne, only to lose in the first round of Wimbledon a week later. So, even after making the finals in Toronto (where the Australian lost to Williams), she went into the U.S. Open under the radar. And her chances didn't look good after being placed in the same half of the draw as Sharapova, who has won all nine head-to-head meetings.