Here are my predictions for the men's quarterfinals at the US Open for 2018. Last year I correctly predicted 3 of 4 women's quarterfinals and correctly predicted 2 of 4 men's quarterfinals. I will also predict the women's quarterfinals.
Rafael Nadal (ESP)  vs Dominic Thiem (AUT) 
Juan Martin Del Potro (ARG)  vs John Isner (USA) . Del Potro is up to a career high of #3 playing someone who is also playing the best tennis of their life. Both Isner and Del Potro have won their first masters 1000 tournaments this year (Isner won Miami, Del Potro won Indian Wells) but tennis results usually come down to match ups. In this one, Delpo has a significant 7-4 head-to-head edge against Isner, who is playing in the 3rd(!) quarterfinal of his career (2nd in New York City).I am pretty sure Delpo's best exceeds Isner's best by a good deal. That all being said, If Isner hits his spots on his serve, there's not much you can do except hope that he misses or you get lucky in the inevitable tiebreaker. Most observers were astonished that Isner was able to get past Milos Raonic in 5 sets with zero tiebreak sets. in the round before while Del Potro dismissed a still-improving Borna Coric in straight sets. Those results may be indicative of the result in this match. Mad Professah's pick: Del Potro.
Marin Cilic (CRO)  vs Kei Nishikori (JPN) . This is a reprise of the 2014 US Open final which was won by Cilic. These two have a closer rivalry than one would expect, with Cilic leading their head-to-head 8-6 with a slight 2-1 edge in their meetings in New York. The reason why I give Cilic the edge in this match is that he has begun to show that he is a big-match player. He has reached two major finals in the last two years (2017 Wimbledon final and 2018 Australian Open final), and even though he lost both of these to Federer, just reaching these finals show how much Cilic's game has improved. While Cilic's level has been rising Nishikori has been stuck in neutral, off the tour either due to injury, surgery or rehab. I don't doubt that Kei is hungry for success, but I think Marin is even hungrier. Mad Professah's pick: Cilic.