The five biggest questions remaining in 2011

1. Can Novak Djokovic finish the year No. 1? Djokovic has yet to lose a match in 2011, having won all 24 times he's stepped on the court this year. That streak includes three wins over Roger Federer and two over Rafael Nadal. The Djoker has already passed Federer for No. 2 in the rankings. Is there a chance he can overtake Nadal? With Djokovic's headstart and Rafa defending max points at all the remaining clay court events and each of the three remaining Grand Slams, the possibility is greater than you might think. A British bookmaking website lists Nadal as a slight favorite in the race. One more Grand Slam by Djokovic could turn things around.

2. Will Caroline Wozniacki finally win a Grand Slam? The female No. 1 better get used to the question. If she stays in the top spot (and the points suggest she will for the� near future) without winning a major, Wozniacki will be hearing this in every interview until she hoists a Slam trophy. (Don't worry, Caro, they used to say the same things about Kim Clijsters too.) The 20-year-old's anachronistic, defensive style doesn't please tennis snobs, who sneer that Wozniacki can't possibly win a Slam without any power (probably while drinking tea with their pinkies extended). Without Venus, Serena or Kim Clijsters, who will though? Maria Sharapova can't get in a serve. Despite recent strides, Vera Zvonareva is still a headcase. Other members of the top 10 haven't played well in ages (Li Na and Sam Stosur, I'm looking at� you). If not Caro, then who?

3. When will the Williams' sisters return? It's been almost one year since Venus and Serena Williams played an event that wasn't a Grand Slam. Since Wimbledon, the sisters have combined to play just two tournaments (Venus in the US and Australian Opens). Given Serena's recent health scare and Venus' nagging injuries, it's legitimate to wonder whether we'll ever see them in the same tournament again. Serena is back to hitting after her foot injury and pulmonary embolism, though her timetable for return is unclear. Venus has been mum on the prospects of her playing the French Open though she was in Germany this weekend to make an appearance with the U.S.'s Fed Cup team.

4. Can Nadal be beaten on clay? One down, four to go. The Spaniard is on a 37-match winning streak on clay and already has one tournament in the bag after defeating David Ferrer Sunday in Monte Carlo. After a respite last year, Nadal is back in Barcelona and plans to play all the major hard court events on the European calendar. He has never completed the sweep when playing Monte Carlo, Barcelona, Madrid, Hamburg (or Rome) and Roland Garros, only achieving it when shortening his schedule last season.

5. Who's the next big surprise? Eleven months ago, Francesca Schiavone was the No. 17 seed at the French Open and may not have even been favored to be the longest lasting Italian in the event. Mardy Fish was ranked No. 97 and figured to be on the downside of his career. And Milos Raonic earned three rankings points after losing to the 479th-ranked man in the world at a Korean F3 event. Who will be the players to breakout in 2011? For the youngsters, I like the WTA's Anastasia Pavlyuchenkova. On the men's side, where a breakthrough may mean a semifinal appearance in a Slam, Richard Gasquet seems due for a repeat of his semifinal at Wimbledon in 2007.

Connie Nielsen Melissa George Cameron Richardson Chandra West Kasey Chambers