Time to get dirty for the game's best

With the clay-court season upon us, it's a good time to evaluate what's at stake for the players who will soon constitute a true "dirty dozen" -- the top six ATP and WTA pros, who will spend much time in the coming weeks trying to wash away caked-on red clay and pink stains from their socks and shorts.

Let's take them in order of ranking:

ATP No. 1 Novak Djokovic: Given what Djokovic did in 2011, it's easy to forget just how tough Rafael Nadal is on clay. Djokovic has said he feels under no obligation to repeat his feats of 2011, but even a slight drop in his level of intensity would open the door for his rivals. Nole has said he's targeting the French Open title, but his prospects of winning it will decline if we see a Nadal resurgence.

No. 2 Rafael Nadal: Can you say "payback"? This is the first time since he was ambushed by Djokovic in 2011 that Nadal will be back on his home turf of Euro clay, starting Monday in Monte Carlo. He's been the champ for seven years in a row (his record at the Monte Carlo Masters: 39-1). Given that, it took guts for Djokovic to enter Monte Carlo. Should they meet in the final, the results will probably have long-term repercussions.

No. 3 Roger Federer: At 30, and with his record, Federer has nothing to prove. But another excellent clay-court season will keep him in good shape physically and mentally for Wimbledon and the Olympic Games, both of which will be on grass. And bear in mind that it was Federer who ended Djokovic's unbeaten streak in 2011 in the Roland Garros semis -- proving, once again, that for most of his career he's been far and away the second-best player on clay (behind Nadal).

No. 4 Andy Murray: He came into the clay-court season last year in a serious slump, and used the red dirt to sort out his game and get back in his top-five groove. This year he'll sally forth more confidently, having avoided another post-Australian swoon. I don't think Murray's full clay-court potential has been tapped yet. Last year he played a sneaky-good four-set match against Nadal in the Roland Garros semifinals. He could surprise everyone and bag his first major on red clay.

No. 5 Jo-Wilfried Tsonga: The Frenchman made great progress over the past six months, but he's had serious trouble cracking the code on clay. Admittedly, this is kind of a French thing; you do well at Monte Carlo or Rome and -- heaven forbid -- the next thing you know your countrymen are thinking you might win at Roland Garros! Tsonga didn't win three matches in a row on clay during the entire spring last year; he needs to show he can perform on the dirt and contend for his national championships.

No. 6 David Ferrer: It's simple. This guy needs to show that he can beat the top players in the top events. Beyond that, it's all been-there, done-that for Ferrer at this time of year.

WTA No. 1 Victoria Azarenka: I don't know why there's so much talk about Azarenka's need to demonstrate that she can play on clay; she won Marbella last year and lost only to players who went on to win the title at every other spring clay tournament but one (Stuttgart, where Azarenka retired during her first-round match). But given her start to the year, she needs to do well on clay only to enhance her chances at the French Open.

No. 2 Maria Sharapova: I'd bet she wants to maintain the momentum she's built up this year, to keep the youngsters ranked below her at bay. And that is a tougher job for her on clay than any other surface. Last year, Sharapova surprised everyone, including herself, when she won Rome. But she has a lot of points to defend and will certainly feel some pressure.

No. 3 Petra Kvitova: She came within a hair's breadth of taking the year-end No. 1 ranking in 2011, but she's been a bust since she made the semifinals of the Australian Open two months ago. She needs to win matches. Many matches. And soon.

No. 4 Agnieszka Radwanska: This young lady has one big problem: It's called Azarenka. Radwanska has lost to the No. 1 four times this year, and she's won every other tournament she's played (we won't count that match she had to surrender via walkover in Kuala Lumpur). Radwanska has to put her foot down and take a stand, because her tricky, counter-punching game is ideal for clay.

No. 5 Samantha Stosur: It's getting to the point that she needs to do something, and pretty quickly, to retain her credibility as a player of the first order -- a reputation she earned with that great win at the U.S. Open last year. You can play your way back into form on clay (just ask Murray, who did it last year), and that's just what this former French Open finalist needs to do.

No. 6 Caroline Wozniacki: The assignment is simple: Stop the bleeding. Wozniacki embarked on the year at No. 1, but she's been eclipsed and has left many thinking that her window of opportunity to win a major is closing -- fast. She needs to show that she can fend off the threats represented by vastly improved players like Kvitova, Radwanska and Azarenka, as well as veterans like Sharapova, Li Na and Serena Williams. It's a tough assignment for the defense-minded Dane.