Milos Raonic says he's unsure whether his sore left knee will prevent him from defending his title at the SAP Open in San Jose, Calif., this week.

Canada's top singles player pulled out of Sunday's Davis Cup World Group tie against France at UBC.

Raonic, ranked 29th, was scheduled to face world No. 6 Jo-Wilfried Tsonga in the fourth match.

Raonic will be in California today, where he was supposed to play an exhibition doubles match with John McEnroe against Gael Mon-fils and Jack Sock ahead of the San Jose tournament. Instead, the 21-year-old from Thornhill, Ont., will undergo further medical tests on his left knee.

"I really have no understanding of what I'm dealing with," said Raonic, who had his left knee taped all week in Vancouver.

"I still need a lot more information and that's going to be a big part of the decision [whether to play in San Jose]. "It will also give me time to consult with my doctor back in Spain.

"First priority is to figure out what the problem is, then go to the people I trust and figure out a solution."

Raonic said the pain was manageable throughout the week, including Friday when he beat Julien Benneteau in straight sets to pull Canada even at 1-1. It felt worse just before the end of the first-set tiebreak in Saturday's doubles, he said, and the decision was taken over-night not to risk further injury.

"This whole week I've been having a little soreness," he said. "A lot of days out of the year you're going to play with some discomfort. [Saturday] really felt like it got worse. It started affecting the main parts of my game, the serve, my first step.

"What I said to the team was, 'I don't care how much pain it is, as long as my health's being looked after. But if it's a matter of not knowing what it is and there being any type of risk at all ... I went through that last year.

"Considering the condition I was in, we felt Frank was a much better [choice]."

Raonic, who endured hip surgery after Wimbledon last summer, defended captain Mar-tin Laurendeau's decision to use him in doubles on Saturday.

Originally, Vancouver's Vasek Pospisil was set to play along side Daniel Nestor for Canada in doubles, but Laurendeau changed course after Friday's singles and selected Raonic.

"Let's say [I didn't play doubles and] it starts hurting after one set in singles today," Raonic said of his knee. "I would have been useless.

"Really, you can't control these things. You try to make the best of it."