Fabio Fognini of Italy upset top-seeded Tommy Haas of Germany 6-4, 6-2 on Friday to reach the semifinals of the Mercedes Cup.
Haas saved four match points before sending a backhand wide to send Fognini into his third semifinal of the year. He lost the previous two, in Acapulco and Monte Carlo.
"It's my second semifinal in Stuttgart, maybe I can go all the way," Fognini said. "I just played my tennis and it worked for me."
Fognini will next play Roberto Bautista Agut of Spain, who advanced when German opponent Michael Berrer retired with a left elbow injury. Agut was leading 6-2, 0-1 when Berrer quit.
Haas, at 35 the oldest player in the top 100, said Fognini played better on the key points.
"I had five break points in the second set and if you don't use them you can't win," Haas said.
Victor Hanescu of Romania also reached the semifinals by beating fourth-seeded Benoit Paire of France 7-5, 6-2.
It's the first time Hanescu has made it into the last four of a tournament since Nice in 2001. He now has a 4-0 record against Paire, all on clay.