Japanese qualifier Go Soeda upset defending champion Stanislas Wawrinka of Switzerland 6-4, 6-4 in the Chennai Open quarterfinals on Friday.
The 120th-ranked Soeda broke in the third game of the first set and the ninth game of the second after twice earlier trading breaks with the Beijing Olympics doubles gold medallist.
"He deserved to win, he was playing better and was putting a lot of pressure on," Wawrinka said. "It happens this is just the beginning of the year. You are looking for matches, looking for rhythm, looking to play a good game."
Soeda will now play top-seeded Janko Tipsarevic in the semifinals after the Serbian beat Belgian wild card entry David Goffin 6-2, 3-6, 6-2.
"I am really happy - my first Tour semifinal and beating the world No. 17," Soeda said.
Second-seeded Nicolas Almagro of Spain and fourth-seeded Milos Raonic of Canada set up a semifinal clash after contrasting quarterfinal victories.
Almagro saved three match points before beating Japanese qualifier Yuichi Sugita 4-6, 7-6 (8), 6-4, while the big-serving Raonic served 15 aces to sweep aside Israel's Dudi Sela 7-6 (4), 6-3.
The 1.96-meter Raonic, who won the ATP Newcomer of the Year award in 2011, lifted his game in the second set after an evenly contested opener.
"Obviously, I am happy with the result," the Canadian said. "There were a lot of things to be happy about, but a lot of things that I need to address for tomorrow.
"Today, I think I served a lot better but I was struggling to choose the right shots. Sometimes I was hesitant and sometimes I was rushing too much, making it difficult for myself."
It was Almagro's first match at the tournament this year, after receiving a first-round bye and Steve Darcis of Belgium pulling out with an injury in the second round.
Sugita squandered his chance to win in the second set tiebreaker, allowing Almagro to close it out on his fifth match point.