John Isner from the US beat compatriot James Blake 7-6 (1), 7-5 (5) to reach the Atlanta Open semifinals for the fourth straight year.
The top seed had to battle hard for the victory Friday with both sets going to the tie-breaker, reports Xinhua.
"A lot of times, I play my best tennis in the tie-break," said Isner.
Isner would face Australian veteran Lleyton Hewitt in the semifinal.