TOKYO -- Canada's Milos Raonic advanced to the last eight of the Japan Open on Thursday after Serbian opponent Viktor Troicki retired from their match while trailing 3-0 in the first set with a right calf injury.
Raonic moved into the quarter-finals of the ATP 500 event after losing in the second round in his first two appearances in 2010 and 2011 -- both to Rafael Nadal.
The hard-serving 21-year-old from Thornhill, Ont., will face Janko Tipsarevic of Serbia in the quarter-finals on Friday after the third seed defeated Swiss qualifier Marco Chiudinelli 6-4, 6-2.
Raonic expressed his regret that Troicki was unable to finish.
"It was a problem he picked up a few days ago," said Raonic, the No. 15 player in the world who is in the battle for a place in the eight-man year-end championships in London.
The last four places will be decided over the next month of ATP play and Raonic has a chance of making the field if he keeps winning.
"I hope (Troicki) has a quick recovery, as he's a good friend," Raonic said. "I had some time to get back onto the court afterwards and get ready for (Friday) as best I can."
Raonic, who is 41-16 on the season with two trophies, now stands 2-0 against Troicki after also beating him this summer at the Rogers Cup in Toronto.
Raonic defeated Tipsarevic earlier this year in a three-hour final at the Chennai Open in India.
Raonic says he has recovered his form after a poor week in Bangkok, adding his current game "in good health."
"It's on the right track again, I'm getting better and better with each match," he said. "I struggled last week but I came here with a different attitude and a different strategy."
Raonic spent part of his day off this week on a tour of the sprawling Japanese capital, visiting a museum where he got to handle a massive samurai sword.
"That sword took me by surprise, it was really heavy. It was special to have this experience, seeing something of the city," he said. "For me, culture is not reading about it but actually experiencing it."
