Rafael Nadal (ESP)  vs Diego Schwarztman (ARG) . Schwartzman showed his mettle in the previous round coming back from being hammered in the first two sets against Kevin Anderson to win in 5 sets. Can the diminutive Schwartzman put an end to Nadal's streak of sets won at Roland Garros? Possibly, yes. Can the Argentine win the match? No. Mad Professah's pick: Nadal.
Marin Cilic (CRO)  vs. Juan Martin del Potro (ARG) . Amazing that the one country that has two men in the quarterfinals is not Spain, France or Italy but Argentina! Del Potro is playing excellent tennis, and was very sharp in his straight set dismissal of John Isner in the round before, but Cilic is an even sterner challenge due to his better movement. However, for some reason the head-to-head between these two Big Boys is skewed way in favor of the Argentine. The two have played twelve times and Cilic has only won twice, with 7 consecutive losses sets including all three of their career meetings on clay. Cilic will be motivated to win this match, but his enthusiasm may be dampened realizing that he gets Nadal as a reward. I think this will probably be a tough 4 or 5 set match, which just gives the winner even longer odds against Nadal in the semifinals. Mad Professah's pick: Del Potro.
Dominic Thiem (AUT)  vs. Sascha Zverev (GER) . This is the popcorn match of this round. Thiem is widely considered the heir apparent to Nadal on clay and Zverev is the breakout star of the Next Generation cohort, having won 3 ATP Masters Shields before his 21st birthday (by contrast, Del Potro just won his first ATP Master Shield in Indian Wells this year) and has earned his #2 seeding. However, Zverev has played three consecutive 5-set matches to reach his very first major quarterfinal, while Thiem has reached the semifinals of Roland Garros for two consecutive years and is the only player to beat Nadal on clay this year. But that win in Madrid was followed by a relatively straightforward loss to Zverev, so this is not an easy match to call. However, it's hard to see how Zverev has enough to go the full distance with Thiem. However since they both know that isn't it possible Zverev could come out and blast Thiem off the court like he did in Spain? Possibly, but that's awfully hard to do on a clay court. Mad Professah's pick: Thiem.