Unseeded American John Isner rallied from losing a first-set tiebreaker to upset seventh-seeded Juan Martin del Potro 6-7 (4), 7-6 (9), 6-3 in a grueling Western & Southern Open semifinal Saturday.
The 22nd-ranked Isner, in his first appearance in the tournament's semifinals, had been 0-4 against the Argentine. He'll play either third-seeded Rafael Nadal or sixth-seeded Tomas Berdych in the final.
The 6-foot-10 Isner needed 2 hours, 47 minutes to improve to 16-3 since retiring from Wimbledon in the second round with a left knee injury. He clinched the win when del Potro sent a backhand from the baseline into the net.