MASON, Ohio (AP) - 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 third-seeded Rafael Nadal, a 7-5, 7-6 (4) winner over sixth-seeded Tomas Berdych.
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.
Top-ranked Serena Williams advanced to the women's final, beating defending-champion Li Na, 7-5, 7-5. In the second semifinal, second-seeded Victoria Azarenka beat Jelena Jankovic 6-4, 2-6, 6-3.
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