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 today'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.