Top-seeded John Isner advanced to his fourth straight Atlanta Open semifinal by beating veteran James Blake 7-6 (1), 7-6 (5) on Friday.
Isner will face seventh-seeded Lleyton Hewitt, the Australian who overcame a slow start to beat third seed Ivan Dodig 1-6, 6-3, 6-0.
In the night quarterfinals, American Ryan Harrison beat Colombia's Santiago Giraldo 6-3, 3-6, 7-6 (2), and second-seeded Kevin Anderson of South Africa topped Uzbekistan's Denis Istomin 6-3, 3-6, 6-3.
The match between Blake and Isner was close in many statistical categories, but Isner extended his ATP Tour-leading tiebreaker record to 23-6 this season. Blake sank to 0-4.
''A lot of times, I play my best tennis in the tiebreak,'' said Isner. ''It's not just coincidence. I'm more aggressive. I need to have more urgency in the rest of the set.''
Isner fell behind 0-3 in the second set, threw his cap to the court, kicked it, and then a couple games later went back on serve when Blake double-faulted on a break point to see his lead shrink to 4-3.
Hewitt turned his match around abruptly to beat Dodig, ranked 36th in the world. Dodig needed just 17 minutes to wrap up the first set, in which he served eight aces and Hewitt won just two points against first serve.
Gradually, Hewitt began timing up serves and when Dodig sent a forehand into the net 40 minutes later, Hewitt had broken for a 5-3 lead.
He rolled from there. The former world No. 1 broke serve all three times in the third, when Dodig won just 42 percent of all points on his own first serve and on a mere 1 of 9 second serves.
''I couldn't get into the match,'' Hewitt said. ''He served fantastic. For a set and a half, I don't think he could play any better. I thought if I could keep it close, he might get tired.''