Perhaps the question heading into next week's French Open should be: "Who can take a set off Rafael Nadal?" instead of "Who can beat Nadal?'"
The Spaniard, dubbed the "King of Clay," is the white-hot favorite to land a record-extending 11th title at Roland Garros.
Nadal seeking 11th title at the French Open
He owns a 79-2 win-loss record at Roland Garros
Possible threats to Nadal are Novak Djokovic and Dominic Thiem
French Open starts Sunday
And given he recently set the men's record for most consecutive tennis sets won -- all on his beloved clay -- it would be some stretch to look elsewhere for a winner.
Take this stunning statistic: Nadal owns a 79-2 win-loss record at the French Open, where the best-of-five set format makes the 31-year-old even harder to defeat. He's only lost to Sweden's Robin Soderling in the fourth round in 2009 and Novak Djokovic in the quarterfinal in 2015.
Plus, Nadal has been busy adding to his trophy haul on clay in the buildup, triumphing in Monte Carlo, Barcelona and then the Italian Open in Rome Sunday.
"Rafa is for me a clear-cut favorite to win No. 11," six-time grand slam winner Boris Becker, who was coaching Djokovic when the Serb downed Nadal in Paris three years ago, told CNN Sport.
"He's by far the favorite. There are a couple of others coming around the block, but I wouldn't even name them because in my eyes if Rafa stays healthy, injury free, I don't see anybody taking it but him."
But if there is to be a monumental upset at the French Open, who might be on the other side of the net? Start with this quintet, which doesn't include the absent Roger Federer.
Djokovic isn't the player he was in 2016, when he won the French Open to become the first man since Rod Laver in 1969 to land four consecutive majors. A loss of focus, intensity and an elbow injury that necessitated surgery this year have all contributed to -- by his standards -- a worrying slump.
However, Djokovic has been Nadal's toughest opponent throughout his career -- still holding a winning head-to-head record and beating him seven times on clay. No one else comes close.
And he was encouraged by his outing against Nadal in the Rome semifinals Saturday. Djokovic tested Nadal prior to succumbing 7-6 (7-4) 6-3. In an indication of the uneasiness Nadal feels when confronting Djokovic, he was often passive and initially let slip a 5-2 lead in the first set.
If they do square off again at the French Open, 12-time grand slam winner Djokovic will surely have benefited from playing Nadal in the Eternal City, despite the end result. It was their first clash since Madrid last year, and the gap was much less than it has been at times.
Djokovic's stint in Rome marked his first semifinal, too, since the Wimbledon warmup of Eastbourne last June. He has reunited with the most influential coach in his career, Marian Vajda, after splitting with tennis legend Andre Agassi and former top-10 pro Radek Stepanek.
But at this stage of his comeback, does Djokovic have it in him to beat Nadal over the best-of-five sets?
Nadal has only lost 36 times on clay in a top-flight career spanning about 13 years.
But Austria's Thiem is one of three players to have bettered the Mallorcan on clay at least three times, following 2004 French Open winner Gaston Gaudio and Djokovic. It was Thiem who ended Nadal's set streak in Madrid this month.
The 24-year-old Thiem is an electrifying shotmaker and clay gives him more time to take the bigger swings he employs. He has the power to rip through Nadal and moves brilliantly, especially on clay.
Yet the world No. 8 needs to progress smoothly in the first week to have any chance of ousting Nadal.
And note that about three weeks after Thiem conquered Nadal last year in Rome, Nadal crushed his younger rival in the French Open semifinals.
The Italian is undeniably one of the enfants terrible of tennis.
Among his indiscretions, Fognini was thrown out of the doubles event at the US Open last year after insulting a female chair umpire in his singles loss. More of that behavior and the tennis authorities could ban him from competing at two majors.
But when keeping his concentration, Fognini is one of the top players in the world on clay, possessing a vast repertoire. His lone grand slam quarterfinal came in Paris in 2011, though he handed a walkover to Djokovic.
The world No. 19 hasn't beaten Nadal three times on clay -- but has done it twice in Rio and Barcelona in 2015.
Fognini's victory in Rio was all the more impressive because he lost the first set -- and since 2014 only three players have upended Nadal on clay after conceding the opener. Fognini's outstanding court coverage was evidenced by his unbelievable pick-up on match point in Rio.
The 30-year-old also knows what it feels like to beat Nadal at a grand slam. In 2015 at the US Open, he became the first man to overturn a two-set deficit against the Spaniard.
In a further boost to his confidence, he also won the first set against Nadal in Rome last week with wife Flavia Pennetta -- the 2015 US Open women's champion -- looking on. A knee issue may have hindered him thereafter.
Unlike Thiem, Djokovic and Fognini, Japan's Nishikori has never beaten Nadal on clay. Nothing to be ashamed of there.
Yet he was on his way to doing so in the 2014 Madrid Open final -- and convincingly.
While the faster conditions in the Spanish capital have never been to Nadal's particular liking, it is still clay and Nishikori led 6-2 4-2 in front of a stunned, partisan crowd.
Unfortunately for the 2014 US Open finalist, he began to suffer from the effects of a back injury, lost the second set and retired at 0-3 in the third.
Nadal's coach, his uncle Toni, admitted afterward: "We don't deserve the victory, he deserves it. He played better than us the whole time. We didn't really come back. He was hurt."
Nishikori, 28, also ran Nadal close in Barcelona in 2016 and defeated him for the bronze medal on a hard court at the Rio Olympics in 2016, but fatigue was likely a factor for the 16-time grand slam winner. Nishikori is a clutch performer, too, in deciding third or fifth sets, holding a 119-38 win-loss record.
He is still returning from wrist surgery -- injuries have been an ever present for the Japanese -- but another tick in the box is that he made the final in Monte Carlo in April, although he lost to Nadal 6-3 6-2.
Keen to find the next big thing in a post Big Four world, the ATP is putting a large chunk of its eggs in the basket of Zverev. Understandably so.
He is only 21 but Zverev -- mentored by his fellow German Becker -- has already won three Masters shields, including in Madrid when he toppled his pal Thiem in the finale. After Federer and Nadal, it's Zverev who comes next in the Masters Series rankings.
Zverev packs plenty of punch, as one would expect from someone 6 feet 6 inches tall. But he moves exceptionally well for his size.
Zverev held a match point against Nadal in Indian Wells in 2016, stretched him to five sets at the Australian Open a year later and took a set off the King of Clay Sunday. If there wasn't a rain delay in the third set when he led by a break, he might have prevailed.
But it would be a tall order indeed for Zverev to beat Nadal at the French Open. He'll start as the second seed and will therefore only encounter Nadal in the final.
And Zverev, for all his prowess on the ATP tour, has never reached a grand slam quarterfinal or beaten a top-50 player at a major.
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