How hungry is Kim for a serve of history?

It was appropriate that one match after she guaranteed her return to the WTA's No. 1 ranking, Kim Clijsters lost in the Paris final to a player outside the top 10.

Yes, as fast as you can say Petra Kvitova, it became clear early in this 2011 season that women's tennis is wide open.

"Kim's on top, but we're in a time where it's not like the Serena era or the Venus era or the Justine era," ESPN analyst Pam Shriver said earlier this week. "It shows you how it's up for grabs. People who don't follow the sport say, 'Well, Serena's No. 1.' Actually, she hasn't played since last July and, hey, it's February.

"What does it say? Work hard and you could win a major or be in the top five by the end of the year. That should make it pretty easy to motivate people. There are a lot of opportunities, great rewards, monetary and title-wise."

Clijsters is No. 1 for the first time since March 2006 -- a gap of 256 weeks, second all time to Serena Williams' 265-week sabbatical -- but, of course, she could lose that spot if Caroline Wozniacki gets to the semifinals in either Dubai or Doha. Only two players have won more than 80 percent of their matches since August 2009: Clijsters and Williams.

With Justine Henin officially retired (for the second time) and Venus Williams hobbled by a hip injury at age 30, a healthy Serena seems like the only player equipped to prevent Clijsters from winning another two or three majors by the end of 2012. But when will Serena, who turns 30 in September, return to health? When will she emerge from her layoff following last summer's foot injury? Officially, she's scheduled to play next month in Miami, but no one is convinced that will happen.

"We've got to start preparing for life after the Williams sisters," said U.S. Fed Cup captain Mary Joe Fernandez. "You can't deny the fact that their bodies are breaking down."

Clijsters has said she would like to leave the game after the 2012 Olympics to have a second child. But could she have imagined a time when she would be the favorite to win virtually every tournament she plays?

"Clijsters lost, what, her first four major finals?" Shriver said. "Now, after retiring, she's won her last four. Who saw that coming? It depends if she has the hunger for tennis history. Financially, she should be fine, but it comes down to this: How much does she love those moments that she had in September and a few weeks ago in Australia? By the [2012] Olympics, if she has five or six majors, how hungry is she for more rarefied air?"

Fernandez, a mother of two, doesn't see Clijsters lingering.

"She said she was leaving before and no one believed her," Fernandez said. "I believe this will be her last full season. She loves her life, but she wants to have more children. I think she'll wind down her schedule in 2012."

Outside of Clijsters -- and Serena? -- who has the best chance to take one of the three remaining Grand Slam singles titles? Wozniacki is the leading contender, but she needs to find a little more offense to go with those dazzling retrieving skills. Clearly, Kvitova, now ranked No. 14, has a bigger game. The 20-year-old Czech lefty beat Clijsters 6-4, 6-3 for her second title of the year. She showed some mental strength in overcoming a match point (against Barbora Strycova) in the second round and eluding a 5-3 third-set deficit to Yanina Wickmayer in the quarterfinals.

"If she continues to play like that," Clijsters said, "she will be top 10 before long. She is so much fitter and moves better than last year."

And what about Vera Zvonareva? At the age of 26, will she break through in a way that Elena Dementieva never did? Sam Stosur has the physical game to do it, but can she sustain her poise in the big moments? Li Na, who has also been to a major final, could contend at Wimbledon. And does Maria Sharapova, still only 23, have a few more Slams in her if she can rebuild her shoulder and serve?

Asked for a short list of emerging stars, Fernandez mentioned Kvitova, Bojana Jovanovski, Julia Goerges and Yanina Wickmayer.

"The state of the game shows you how hard it is to stay healthy week in and week out," Fernandez said. "How the new generation handles their schedules and their training will go a long way toward determining who's ultimately successful."