TOKYO (AP) -- Japanese wild card Tatsuma Ito upset Australian Open champion Stan Wawrinka 7-5, 6-2 in the first round of the Japan Open on Tuesday.
The No. 103-ranked Ito converted all four of his break-point chances to dispatch top-seeded Wawrinka at Ariake Coliseum.
He moved on to meet Benjamin Becker of Germany, who was leading Jarkko Nieminen 7-5, 4-1 when the Finn retired due to fatigue.
''It is the first time I have beaten a top-five player,'' Ito said. ''I tried my best on every point, and I was very focused. I was a little nervous, but I stuck to my game, and I finished well.''
Wawrinka, who won his Grand Slam breakthrough title at the Australian Open in January, is ranked No. 4 and could have ensured a spot at the ATP Finals by reaching the final in Tokyo.
''It was not a good day at the office,'' Wawrinka said. ''He started well, and then I was trying to come back in the match. First-round matches are never easy.''
Third-seeded Milos Raonic of Canada beat Bernard Tomic of Australia, 7-6 (3), 6-3 in their first meeting.
Raonic, a two-time runner-up at Tokyo, will next face Austrian Jurgen Melzer, who was leading 7-5, 4-1 when Edouard Roger-Vasselin of France retired due to a right leg injury.
In another upset, Michal Przysiezny of Poland rallied from a set down to defeat fifth-seeded Jo-Wilfried Tsonga 4-6, 7-5, 7-6 (9).
Also, Jeremy Chardy of France and Donald Young of the United States were winners.