Make-or-break time for Rafael Nadal

Rafael Nadal owns 43 career titles on clay, but will his pedigree be enough to get him back on track? Julian Finney/Getty Images

It was a glorious month of March if you happened to be Novak Djokovic or Victoria Azarenka. They won the prestigious events in both Indian Wells and Miami, an exceedingly rare double-double on the American hard courts.

Now, at least as far as the surface is concerned, it's time for something completely different.

Heading into the palate-cleansing sorbet that is the nine-week spring clay season featuring no fewer than 25 professional events, this much we know:

  • The No. 1-ranked Djokovic is unstoppable at the moment. His only loss in 2015, technically, is a retirement in Dubai due to an infected eye.

  • Azarenka, whose ranking has skipped up to No. 5, is the best player on the women's side. At 34, Serena Williams is, ominously, starting to act her age; the WTA's No. 1-ranked player hasn't won a tournament since August.

  • Roger Federer, also 34, will make his return next week in Monte Carlo after undergoing arthroscopic knee surgery nearly 10 weeks ago.

And here's what we don't know:

Whether 14-time Grand Slam singles champion Rafael Nadal, on the cusp of 30, will ever win another major.

Looking dizzy and wretched, he retired from his first match in Miami against Damir Dzumhur. On March 29, he was back in Mallorca, Spain, and tweeted, "Home now & feeling good. Thanks for all your messages of support."

If this spring doesn't go better than last year's, there may be more messages on the way.

Rafa, it must be said, looks tentative and a half-step slow, and he has struggled recently by his enormous standards. The degree of difficulty his physical style of play requires appears to have taken the predicted toll on his body. As a public service, we'll tell you that 2015 was the first time in 11 years that Rafa didn't win at least one major and a Masters title. Moreover, his 11 Grand Slam match wins were his lowest total since 2004.

The good news: The King of Clay is back on the dirt, where he has always enjoyed his best footing. Nadal has played two clay events so far this year. He lost to 22-year-old Dominic Thiem in the semifinals of the Argentina Open, then fell to Pablo Cuevas in the semifinals of the Rio Open. Rafa enters Monte Carlo without a title for the first time since 2012. Interestingly, he won Monte Carlo that year -- and the other three years (2008, 2010 and 2011) in which he entered the event winless.

Like Rafa's other clay-court statistics, the numbers are going the wrong way. From 2005 to 2012, he won Monte Carlo eight times in a row and built a career record of 44-1. Since then, he has gone 9-3 on the Mediterranean.

The last time Nadal won a Masters championship? Madrid, in 2014. Since then, he's 0-for-13, including a semifinals loss to Djokovic in Indian Wells. That was Djokovic's 27th Masters shield, tying him with -- guess who? -- Rafael Nadal. Now Djokovic has 28, the all-time record.

This is an important juncture for Rafa, who desperately wants to put himself in position to compete for his 10th title at Roland Garros. Nadal is a staggering 70-2 at the French Open, but was dispatched in straight sets in last year's quarterfinals by Djokovic.

Federer, too, faces questions as the play moves to clay.

After losing in four sets to -- who else? -- Djokovic in the semifinals of the Australian Open, the Swiss had some work done. Video of his spirited practices has made the rounds, but this isn't how he imagined the year would go.

Originally, Federer planned to skip all of the pre-French clay events. Now, according to his agent, Tony Godsick, he will play Monte Carlo, then decide whether to appear at Madrid and Rome, also Masters events. It's possible he will play one of those events, which fall back-to-back on the ATP calendar.

Serena isn't thought of as a clay-court wizard, but she is the active leading player, with 12 clay-court titles. Two of those came at Roland Garros, in 2013 and 2015. Maria Sharapova, who is second among active players with 11 titles but is sitting out because of a drug suspension, won in Paris in 2012 and 2014.

Williams' schedule currently calls for her to play Madrid and Rome.

The only woman to win two spring clay championships a year ago, Angelique Kerber, is ambitiously scheduled to play four pre-French events: Charleston, Stuttgart, Madrid and Rome. Madrid, which runs May 2-8, is the only event that carries the WTA's Premier Mandatory label.

Last year, Serena was 7-2 in the clay warm-up to Paris, losing to Petra Kvitova in the Madrid final and losing her second match in Rome to Christina McHale. And then Williams ran the table in Paris, beating Lucie Safarova in the final.

The leading spring storyline, of course, will be Djokovic and his pursuit of his career Grand Slam with a first-time title in Paris. Last year, he advanced to the final -- after defeating Nadal in the quarters and Andy Murray in the semifinals -- but Stan Wawrinka played like a man possessed and denied him.

Djokovic is the overwhelming favorite in Monte Carlo, where he has won two of the past three years. Nine of the ATP's top 10 players (sans Kei Nishikori) will be in action. One of them is Wawrinka, who was Monte Carlo's champion in 2014. That title remains his only Masters victory in 83 career attempts.

These are heady times for Djokovic. He just passed Federer as the ATP's all-time leading money winner, and the Serb will enjoy another, almost unfair, benefit in Monte Carlo. It's now his hometown tournament. Yes, a home-field advantage.

Could he make it 29 Masters titles? History would suggest Nadal is the key man standing in his way.

But is that notion -- along with Nadal's mastery of clay -- simply history?