Isner overcomes Tiafoe, will face defending champ Garin in Houston semifinals

The semifinals of the Fayez Sarofim & Co. U.S. Men's Clay Court Championship have been set, with John Isner battling past Frances Tiafoe on Friday night to secure the final spot.

Isner overcame a second set comeback from his compatriot to reach the final four, advancing with a 6-4 2-6 6-3 victory. The towering American hit 16 aces in the two hour slugfest, winning 80% of points behind his first serve. Isner's serving was instrumental in claiming the opening set, as he hit 9 aces and saved all three break points faced.

However, Tiafoe stunned the Houston crowd by breaking the Isner serve, not once but twice in the second set. Furthermore, the sixth seed saved all five break points faced, and set up a decider against his good friend.

With a spot in the semifinals on the line, it was Isner who broke through the World No.30's defense at the second time of asking. The 6'10 giant then maintained his composure, before clinching the match and advancing to his second ATP singles semifinal of the year.

Isner will face defending champion Christian Garin in the final four, as the fifth seed outlasted Taylor Fritz in their three-set quarterfinal clash.