Chennai: Defending champion Stanislas Wawrinka of Switzerland on Friday crashed out of the Aircel Chennai Open as he was shocked by qualifier Go Soeda of Japan in the singles quarterfinal.

Wawrinka, playing only his second game of the season having earned a first round bye, lost 4-6, 4-6 to 27-year old Soeda, who became the first ever Japanese player to enter an ATP World Tour semifinal.

In a match that lasted just over 100 minutes, the Swiss, ranked 17 in the world, looked off colour and rusty and Soeda capitalised on the opportunity as the Chennai Open yet again proved to be a quagmire for defending champions.

In the 17 editions played so far, only Spaniard Carlos Moya and Croat Marin Celic have successfully defended their singles titles.

Prior to Friday's quarterfinal, Soeda had a 0-8 record against top 20 players, but he put that to rest with the win against Wawrinka.

"I am very happy. He is world number 17. Of course, I am happy," Soeda said after winning the match.

The Japanese player said the partisan support for Wawrinka, a popular figure here, had "not been a big deal" for him. Soeda also said he had improved his forehand this season.

Hustling in at the net regularly and aided by Wawrinka's erratic play, Soeda broke his opponent in the third game of the first set and games three, seven and nine in the second.

Wawrinka did fight back in the second set breaking Soeda in fourth and sixth games but that was not enough as the Japanese broke him back in the seventh before winning the next two games and the match.

In the first set, Wawrinka, the third seed, missed an opportunity to break Soeda in game two, and again in game two of the second set.

Wawrinka's backhand returns, so often his strength, went woefully long today and his serve was also not as big a factor in the match as was expected as Soeda's hustling tactics put him under pressure.

Soeda too missed two breakpoints each in seventh and ninth games in the first set but did enough to capitalise on Wawrinka's errors.

In the semifinals, he will face either top seed Janko Tipsarevic or Wildcard David Goffin.

Wawrinka was gracious in defeat, saying the better player won.

"He deserved to win. He played with a lot of confidence. I couldn't find my rhythm and didn't have enough confidence in my game. But that's life and tennis," the third seed said after losing 4-6, 4-6 to Japanese qualifier Soeda.

"It's just the beginning of the year. I've been playing really good in practice."

The Swiss star said he hoped to come back to Chennai next year.

"It's a great tournament to come to. I've been coming here for four years, so I'd like to come back," Wawrinka said at the post-match press conference.