Alexander Zverev versus Dominic Thiem

Alexander Zverev and Dominic Thiem are the two most consider to be the most likely candidates behind Rafael Nadal to take the title here and have thus far lived up to their seeding.  By the time play draws to a close on Tuesday, however, only one of them will still be in the title hunt.  In spite of being the slightly lower-seeded of the two, many are apt to look to Thiem as the likely victor.  He is more at home on the dirt than the German, produces heavier shots, and his backhand does a better job of finding angles and creating space on this surface.  But Zverev can pack a punch of his own from the ground, and at 6'6” should start off in the driver's seat on his own service games. 

He has to be committed to staying up on the baseline though, or Thiem is likely to wear him down and make him pay.  Thiem has been able to get the better of the second seed on four of the six occasions when they have met, including here two years ago.  Furthermore, he has twice before been to the semifinals at Roland Garros, so he is likely to be more comfortable with the situation than Zverev, who is contesting a major quarterfinal for the first time in his career.  If Zverev still has some gas in the tank after coming through three consecutive five-set matches and can temper his nerves, then he could avoid the upset by taking care of the Austrian much as he did in the final of Madrid a few weeks ago.  If not, then the chips are stacked a little more in Thiem's corner, and although on paper it would be an upset, Thiem should be the competitor expected to advance.

Novak Djokovic versus Marco Cecchinato

There were a lot of question marks surrounding Novak Djokovic coming into Roland Garros, and though he has yet to provide all of the answers, there are positive indications that his game is moving in the right direction.  He has yet again worked his way into the quarterfinals, where after battling past the likes of Roberto Bautista Agut and Fernando Verdasco, he might feel like he has caught a break.  Standing between him and a spot in the semifinals is the unheralded Marco Cecchinato.  One could be forgiven if not familiar with the Italian.  Prior to this event, Cecchinato had never won a Grand Slam match, so to say that he is in uncharted territory would be a gross understatement. 

He has played some good tennis to get here though, knocking off two Top 10 seeds in Pablo Carreno Busta and David Goffin and will not be ready for his Cinderella story to end.  The good news for Cecchinato is that clay is his preferred surface, so that should help his comfort level on the court.  The bad news is that his serve is his favorite shot, and he is facing one of the greatest returners in the history of the sport.  In addition to that, Djokovic is vastly more experienced at this level, and there is nothing Cecchinato does that Djokovic does not do better, albeit the Serb has not yet tapped into his top-shelf brand of tennis.  All told, barring a phenomenal performance from Cecchinato or a let-down from Djokovic, the twentieth seed should move through to the semifinals. 

Sloane Stephens versus Daria Kasatkina

Several seeds and tournament favorites have been sent packing from the bottom half of the draw, but one who remains is reigning US Open Champion Sloane Stephens.  In fact, she is now the highest seeded player left in the bottom half and is increasingly looking like the favorite to emerge from it.  After pulling off a Houdini act against Camila Giorgi, she barely broke a sweat in dispatching Anett Kontaveit to reach the quarterfinals and will be hoping to replicate that form against her next opponent, Daria Kasatkina.  But the tenth seed will not be taking Kasatkina lightly.  The Russian has really announced her arrival this season by accumulating a number of notable victories, including a win over Caroline Wozniacki in the last round to set up this clash.  Because of her own speed and anticipation skills, her court coverage is arguably equal to that of Stephens, and she can do more with the ball when put in awkward positions.  She also sports more variety in her game, which could enable her to keep Stephens on her toes and feeling uncomfortable out there.  No question Kasatkina has to serve better than she did against Wozniacki, however, if she wants to be able to utilize everything in her bag of tricks.  If not, Stephens will make her pay by dictating from the start. 

Stephens also more regularly plays with greater power from the ground, so Kasatkina must inject all of her various spins and slices to keep the ball out of Stephens's strike zone and avoid allowing the American to get into a rhythm.  She knows she can do this, because she easily defeated the tenth seed on her way to the final of Indian Wells.  But Stephens did get the better of Kasatkina on the dirt in their other previous encounter, and there is no discounting the fact that Stephens is a major champion and has contested matches of this magnitude more often than the Russian.  If Kasatkina can control her nerves and play within herself, then this has the makings of a highly entertaining match that could more than conceivably end in an upset.  If not, then expect Stephens to continue where she left off against Kontaveit to move one step closer to the Roland Garros crown.