John Isner, seeking his second title in as many weeks, booked a semi-final matchup with Dmitry Tursunov on Friday at the $1.76 million ATP and WTA Washington Open.
US eighth seed Isner, who won last week in Atlanta, fired 18 aces to defeat Cyprus' Marcos Baghdatis 6-7 (5/7), 6-4, 6-4 while Russia's Tursunov outlasted Australia's Marinko Matosevic 6-3, 4-6, 7-6 (7/4) in another quarter-final at the hardcourt event.
"I was pretty confident even though I lost the first set," Isner said. "I know I'm not going to win every tie-breaker. I was in a good rhythm and serving well.
"I wanted to make him beat me. I didn't want to lose my mind out there and I held it together pretty well over the last two sets."
It will be the first ATP meeting for Tursunov and Isner, who is feeling confident three weeks ahead of the US Open.
"It gives me a lot of confidence," Isner said of his Washington run. "I have won a lot of matches this year and I have a really good feeling going into the rest of the season."
Top seed Juan Martin Del Potro of Argentina was set to play South African seventh seed Kevin Anderson in a later match, with the winner to face either German third seed Tommy Haas or Bulgarian 11th seed Grigor Dimitrov in the semi-finals.
French fourth seed Alize Cornet advanced to the women's semi-finals with a 7-6 (7/5), 6-2 triumph over Romanian fifth seed Sorana Cirstea.
"Today was the first time I beat Sorana on hardcourt," Cornet said. "It's an amazing win. It means I'm improving my game.
"It was hot and the courts were fast. The balls were bouncing everywhere but I was able to handle the conditions very well."
Cornet will next face Germany's Andrea Petkovic, who ousted Argentina's Paula Ormaechea 4-6, 6-1, 6-3.
"I've never won against Cornet so that will make a really nice challenge," Petkovic said.
Also moving on was Russian third seed Ekaterina Makarova, who won the first game before Romania's Monica Niculescu retired with a left wrist injury.
Makarova will face either German top seed Angelique Kerber or Slovakian seventh seed Magdalena Rybarikova for a spot in Sunday's final.
Isner never faced a break point but dropped the first set in a tie-breaker after netting a drop shot to lift Baghdatis level at 5-5. The Cypriot hit a service winner and Isner followed by swatting a forehand wide to surrender the set.
Isner, seeking his eighth career ATP title, broke Baghdatis in the seventh game of the second and third sets to win after one hour and 56 minutes.
"I'm not looking forward to facing him," Tursunov said. "He has been serving well lately. He has a lot of confidence right now."
Matosevic broke Tursunov to force a third set, then saved the first four break points the Russian managed.
Tursunov, despite 13 double faults, turned the tables and denied the 83rd-ranked Aussie on three break-point chances until they reached a tie-breaker that was in doubt until the Russian took the last three points.
Tursunov, ranked 61st, seeks his first semi-final since February at Marseille. That was his first appearance in the last four since winning in 2011 at s-Hertogenbosch.