PARIS -- For the sixth time, Roger Federer and Rafael Nadal will face off at Roland Garros. Nadal is 5-0 in their previous meetings, but will Federer have the upper hand this time around in his return to the French Open for the first time since 2015? Our experts preview Friday's semifinals clash:

Which is more impressive: Federer's overall 20 Grand Slam singles titles or Nadal's record 11 French Open titles?

ESPN TV analyst and seven-time Grand Slam singles champion John McEnroe: Both records are amazing. Obviously, what Nadal has done in France is unprecedented, and I can't even imagine in my wildest dreams it will happen again. But, overall, Roger has been so good for so long, he's stepped up at all of the Slam events and has had success on every surface/court for a long period of time. So, while it's extremely close -- you'd be happy to take either one of them -- I'd say Roger's body of work is a little bit more impressive.

ESPN.com tennis reporter Peter Bodo: Federer, the all-time men's Grand Slam singles title winner, has a wonderfully diverse record. He has won eight Wimbledon titles, five US Open crowns (consecutively, no less, from 2004 to '08), six Australian Opens and a one French Open championship. One detail that may leap out from among these honors: Why just one French Open? The answer is obvious: Nadal. The King of Clay has beaten Federer in all five of their meetings in the French Open and is a mind-boggling 91-2 at Roland Garros.

While Federer may go down in history as the sport's most versatile player, it isn't difficult to visualize either Nadal, Djokovic or some future player catching and surpassing him in the Grand Slam derby. But does anyone really believe Nadal's French Open record will be surpassed? I can't. It's the most remarkable record in tennis.

ESPN.com contributor Simon Cambers: So hard to say. Nadal's record of 11 French Opens is a joke, and one that surely will never be broken. Mind you, we said that about Pete Sampras when he reached 14 slams and now he's only fourth all time. Federer's overall record is incredible and, for me, he just about edges it, because he has been able to win many titles, on all surfaces. Winning 11, and maybe 12, French Opens is ridiculous, but because it is all on clay, one unique surface, Federer just about takes it.

ESPN.com senior writer Bonnie D. Ford: I am loath to attribute more weight to either of these two incredible accomplishments. But if you're asking which one will never be surpassed, it's Nadal's. He's withstood challenges from the most talented and motivated players in the world year after year, and he has made the prospect of beating him seem psychologically and physically insurmountable. And it's not just about what he does in the semifinals and final. The way he generally takes care of business earlier in the draw has helped him conserve energy for the most important moments.

Roger Federer and Rafael Nadal have faced off five previous times at Roland Garros, with Nadal winning each of them.Federer, however, has won five in a row overall against his rival. Pierre-Franck Colombier/AFP/Getty Images

Federer has won his past five matches against Nadal, but they have not met on clay since 2013 in Rome or here at the French Open since 2011. Does Federer have a psychological edge, even on clay?

McEnroe: Roger has been able to get a little bit of a psychological edge these past couple of years, since he's added to his game by becoming more aggressive, trying to take the net away from Nadal and shorten the points. That's thrown off Nadal's rhythm and helped him win those last five matches. He's going to need to do that Friday, which is obviously a lot tougher to do on clay. Federer is going to need to keep the points short, go for his shots and move forward a lot -- and it's hard when you're slipping and sliding on clay and you're playing the master of all masters on the surface in Nadal. At Federer's age [37], it would be a major accomplishment if he can win this match, even for him.

Bodo: Psychological edge to Federer? I'd say it's more a case of Nadal relishing the opportunity to finally extract a little payback. And who could blame him? It's understandable that Federer made himself scarce on clay in the past few years. One of the great lessons he took out of his six-month hiatus following minor knee surgery in 2016 is you can't play them all -- at least not if you hope to win a good number of them.

In avoiding clay, Federer was also avoiding Nadal, who holds a 23-15 edge on Federer even though they haven't met on clay since the Italian Open final of 2013 (Nadal won that one, 6-1, 6-3). True, Nadal beefed up his series lead with a lot of clay-court wins early in the rivalry and, unlike Federer on clay, he did not always go deep enough to meet Federer on hard or grass courts. That recent 5-0 advantage to Federer? It's less intimidating for Nadal than jet fuel for his psyche.

Cambers: This is the most interesting part of the matchup for me. On hard courts, with the help of his bigger racket, Federer has reinvented his game. His backhand is twice as good as it was when he was winning three slams a year and his attitude against Nadal has changed, becoming more aggressive, especially on returns. The question is whether he can do that on clay, where Nadal has slightly more time to recover and his own shots have that bit more bite. Federer has to play at his absolute best to have a chance, whereas Nadal could play below his best and win this match. Nadal will win.

Ford: I'll let Federer answer this instead. When asked Tuesday about the looming matchup, he said, "There is always a chance,'' and went on to describe how Nadal could be sick or struggling, or it could be windy, or it might rain. Translation: If Nadal is Nadal on center court at Roland Garros, forget it.

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Where does the Nadal-Federer rivalry rank among the great rivalries in tennis history?

McEnroe: Roger and Rafa's rivalry has been awesome, no question. There have been times when people have talked about who is the greatest player ever and it's gone from one of them to the other, at least for me, a couple of different times. They've played everywhere, multiple times, and it's ironic that late in their respective careers that Roger has finally figured how to get the edge and how to deal with Nadal and that left-handed, topspin forehand and wide serve on the ad court.

Bodo: The greatest rivalry in tennis is still the one between Chris Evert and Martina Navratilova, which finished with Navratilova leading 43-37. That record is unlikely to be eclipsed in our era, although the Federer-Nadal rivalry has some of the same identifying characteristics. Both series feature a tremendous contrast in styles, their surface of choice and personas.

Focusing exclusively on the men in the Open era, the Pete Sampras-Andre Agassi rivalry has been the only one to achieve the kind of hype Federer and Nadal generate. The numbers are similar: Sampras finished 20-14 over Agassi. The John McEnroe-Jimmy Connors rivalry also hit many high notes. They also embodied great contrasts, but, perhaps more important, both were American at a time when the U.S. ruled tennis. McEnroe prevailed, also by 20-14.

Cambers: It's right up there. Bjorn Borg-John McEnroe was great, Connors-Ivan Lendl, too, while Martina Navratilova and Chris Evert met 80 times (61 in finals), which is crazy. But the Federer-Nadal rivalry is so great because of the contrast in styles; the artist against the bull, the attacker against the counterpuncher (though Nadal is much more than that). Like any great rivalry, they have brought out the best in each other, and though Nadal and Novak Djokovic have actually played each other more times, these two set the standard.

Ford: I grew up with Evert-Navratilova and Borg-McEnroe-Connors, and I cut my teeth as a tennis writer on Sampras-Agassi. Watching their story arcs over the years was thrilling, riveting and emotional. But Federer-Nadal has taken the sport to another level globally/socially/culturally. They've transcended all borders. If you ask any hard-core tennis fan their allegiance, they almost always have an instant answer. I'm old enough to remember when the kids in my neighborhood insisted everyone choose sides between the Beatles and Rolling Stones. It's like that.

It's not just Nadal's unique lefty forehand Federer will have to be worried about; Nadal's backhand can also cause problems. JB Autissier/Panoramic/Icon Sportswire

What is your favorite moment from this rivalry?

McEnroe: My favorite was commentating and being a tiny part of their amazing match at the 2008 Wimbledon men's singles final. You had two contrasting personalities, style of play, the way they looked, the way they operate, the way they expressed themselves -- and it all came together at the All England Club. It looked like they could barely play any longer and the match ended in a way no one expected, with Rafa being able to pull it out late in the fifth set in a 6-4, 6-4, 6-7 (5), 6-7 (8), 9-7 win. That was the most amazing thing I've ever seen between the two of them.

Bodo: In May 2006, Federer and Nadal played one of the greatest matches in tennis history, an Italian Open Sunday final that ended with Nadal triumphant, 6-7 (0), 7-6 (5), 6-4, 2-6, 7-6 (5). Both men were entered in the Hamburg Masters (which has since vanished from the calendar), which began the following day. They decided they weren't going to have any part of that after their five-hour Italian ordeal and decided to withdraw. Both warriors appeared with tournament officials for the formal announcement, looking ragged but proud. They received a hero's welcome. The loss of the top two seeds was a serious blow to the tournament and triggered the ATP to adopt a best-of-three set format for Masters finals.

Cambers: It would be easy to say the 2008 Wimbledon final, but I have two, if that's allowed. One, when Nadal produced arguably the most dominant performance in the 2008 French Open final after demolishing Federer 6-1, 6-3, 6-0. The second was when Federer beat Nadal to win the 2017 Australian Open title. The first was simply a massacre on the clay; the second, an example of the new Federer, when he attacked on his backhand, and returns, to deny Nadal the title.

Ford: Why not watch, without a doubt, their greatest mutual challenge:

What one shot does each player have to prep for against his opponent?

McEnroe: For Roger, it's that high backhand from Nadal; he knows he's going to get it, and it's a question of how he's going to deal with it. For Rafa, it's going to be, "How am I going to deal with Roger's serve?" Nadal has chosen to stand way back; but is he going to continue to do that, knowing Roger is going to move forward and try to cut off his return, or is he going to stand a little closer and mix it up? It's going to be interesting to see who will be more effective at doing the one thing they really need to do well to win the match.

Bodo: Nadal needs to dial in his return game. Federer has a superb serve. He isn't even in the top five at Roland Garros when it comes to the ace count, but he's No. 2 in winning first-serve points. Put that down to Federer's precision, placement and variety. Nadal surely will try to push Federer back and force him into baseline rallies if he can read that magnificent serve and control of a reasonable number of points with his return.

The Nadal forehand is a unique shot. There's never been anything quite like that wicked, lefty topspin drive that literally leaps up off a court at an opponent. Getting caught in rallies way back behind the baseline with Nadal whaling away from the forehand side is a recipe for disaster. Federer may have to gamble and adopt the counterintuitive strategy of going right to Nadal's forehand to pull him wide, thereby opening up the court.

Federer's excellent serve -- and potentially his serve and volley -- could be a key to beating Nadal. Gwendoline Le Goff/Panoramic/Icon Sportswire

Cambers: Federer will prepare for the Nadal serve, especially the serve out wide on the ad court. In the past, Federer was guilty of slicing it too often, allowing Nadal to get onto his forehand. Now, he's better at hitting through the backhand, and he'll need to do that. For Nadal, he will prepare for Federer to come forward, but it'll be the Federer serve and volley that could be the key. If Nadal stands as deep as he usually does on clay, the serve and volley, especially on the deuce court where he will attack the backhand out wide, could be very effective for Federer.

Ford: Variation and well-constructed point geometry will be the key for Federer. He has to try to own everything but the baseline, and to quote him, be "fearless ... to take on the spinny balls, the sliding balls, the kicking balls.''