TOKYO- Tatsuma Ito followed the winning example of compatriot Kei Nishikori as the number 103-ranked local dumped top seed Stan Wawrinka out 7-5, 6-2 in the first round of the Japan Open on Tuesday. Ito, finalist at a Challenger event a fortnight ago in Turkey, showed no fear as he imposed his game on the Swiss world number four who won the Australian Open in January.

US Open finalist and last week's Kuala Lumpur ATP winner Nishikori is seeded fourth at the home event he won in 2012 and opens his singles campaign Wednesday. Wawrinka stands next in the queue to qualify as fourth man into the eight-player World Tour Finals in London in November. The Swiss was puzzling through what went wrong with his game in the 79-minute loss, which will make him wait another week to likely enter the year-end field, at the Shanghai Open.

"It was certainly not a good day at the office. I'm not happy about the result," said Wawrinka, who smashed a racquet in his frustration on court. "I have to see what is wrong and try to change it before Shanghai. It was a bad match from my side. I felt slow on the court and was not moving well. It's tough to say exactly what went wrong. I've seen Ito play and knew his game. I allowed him to play aggressively and he had a good match. It's tough to say what happened to me but I have to work it out and make corrections before Shanghai." Wawrinka said he was not worried about his London position -- only the state of his game two weeks after helping his nation into the Davis Cup final against France. "I'm not worried about qualifying, I just need to start winning some matches. It's a long season and we all are a bit tired. I was feeling OK, I don't know why I played this poorly."

Fourth seed Nishikori will take his growing confidence into the concluding weeks, with hopes of becoming the first Asian man to qualify for the season final. "I'm sixth now (in the season points race) and I'm really hoping to qualify," he said after a doubles win. The Japanese player said it was the first year he had the chance to reach the final. "It's something that every player wants to play. I'm happy about standing sixth but I have a lot of work over the next weeks," he said. "I'm pleased to be in this position but the race is very close and a lot of players are trying to earn a place. Some good results over the rest of this Asian swing will help, I'm hoping to do well."

Nishikori will open his singles campaign against Croatian Ivan Dodig on Wednesday in front of his home crowd. The 24-year-old is Japan's only player in the ATP top 100, with the other six Japanese players still ranked within the top 170. Nishikori won the Tokyo title in 2012 and is the only Japanese to lift the honour.

In first-round results, German Benjamin Becker beat Kuala Lumpur semi-finalist Jarkko Nieminen as the Finn retired trailing 7-5, 4-1. Two more players, Frenchman Edouard Roger-Vasselin and sixth seed Roberto Bautista Agut also failed to finish. France's Gilles Simon saved six match points in the second set as he held on for the 4-6, 7-6 (9-7), 2-1 win when his opponent could not go on.