Top-seeded Janko Tipsarevic of Serbia out-rallied Fernando Verdasco of Spain from the baseline to win 7-6 (5), 6-4 and move into the Thailand Open semifinals on Friday.
Tipsarevic set up a match with 2009 champion Gilles Simon, who won the all-French quarterfinal with Gael Monfils 6-4, 6-1.
''It was really tough but I expected it. I have played Fernando 5-6 times,'' said Tipsarevic, who improved to 4-2 against the Spaniard. ''It's always been battles from the baseline. He made me suffer, and I ran a lot today.''
He rallied in the tiebreaker from 5-2 down to tie it at 5. Then the fifth-seeded Verdasco made two forehand errors to lose the 52-minute opening set.
Tipsarevic saved several break points to hold for 4-4, broke to go ahead and won the quarterfinal on another Verdasco forehand mistake.
Tipsarevic, chasing a spot in the eight-man ATP Finals, expects a tough match with Simon.
''I have played Gilles many times. I lost more than I won,'' he said. ''He is the previous champion here. He knows the surface. He keeps coming back every year. I'm here for the first time. I'm expecting a tough match like today.''
The fourth-seeded Simon benefited from a recurrence of Monfils' right knee injury, the same problem that kept him off the tour for four months until recently.
Simon came back from 2-0 down to win the first set, and had his right foot re-taped to start the second set. He lost the first game on serve, but quickly regained control to reach his sixth semifinals of the year.
Another Frenchman, second-seeded Richard Gasquet, made it to his third semis this year in handling eighth-seeded Bernard Tomic of Australia 7-6 (5), 6-4. Gasquet secured the one break from just two chances, and saved all three break points he faced.
Beating Grigor Dimitrov from 7-5, 5-2 down the day before gave Gasquet confidence against Tomic.
''Yesterday I was lucky to win, today I played better,'' Gasquet said. ''It was a tight race in the first set. I did it. I felt more confident. That's what made the difference.''
