Stanislas Wawrinka has admitted that he has no complaints following his shock defeat to Tatsuma Ito in the opening round of the Japan Open.

The Australian Open champion suffered an early exit in Tokyo on Tuesday, losing 7-5 6-2 to the world number 103.

Despite being on the wrong end of such a surprising result, Wawrinka believes that he did not play well enough to progress.

"It was not a good day at the office," the Swiss is quoted as saying by the ATP's official website. "He started well and then I was trying to come back in the match. First-round matches are never easy. He played well, particularly at the end of the first set when he was very aggressive."

Ito's reward for seeing off Wawrinka is a second-round encounter with German world number 62 Benjamin Becker.