Milos Raonic emerged as the only Canadian winner at the Western & Southern Open on Wednesday after the fifth seed defeated American Robby Ginepri to advance to the third round.

Raonic, from Thornhill, Ont., beat Ginepri in straight sets, 6-2, 6-2.

Wimbledon finalist Eugenie Bouchard of Westmount, Que., meanwhile, suffered another hard court disappointment in losing to Russian Svetlana Kuznetsova 6-4, 3-6, 6-2. Earlier, Vancouver's Vasek Pospisil pushed Roger Federer to a third set before falling to the tournament's second seed.

Raonic says he was pleased with his performance, but is looking for improvement.

"I felt great after the first match of the week," said the Wimbledon semi-finalist. "These were much different conditions than last week at the Rogers Cup.

"But I came up with the right mentality and was able to execute well. I wasn't particularly nervous. I knew how I'd prepared and what to expect. I was able to break right away and that made things go well form the beginning."

Federer, third in the ATP world rankings, is coming off an appearance in the finals of the Rogers Cup in Toronto. Federer lost that match to Jo-Wilfried Tsonga.

The Swiss tennis star beat Pospisil 7-6 (4), 5-7, 6-2 in the second-round match on centre court to become the only man to reach 300 wins at the Masters 1000 level in men's singles.

33 winners

Pospisil beat Radek Stepanek in the first round in Cincinnati a week after losing his opening match at the Rogers Cup. He had 33 winners and 37 unforced errors against Federer.

Pospisil played tough against Federer, forcing a tiebreaker that he ultimately lost on a forehand error. Pospisil secured the second set when Federer missed on a forehand cross-court.

The third set was all Federer, with Pospisil broken twice on the way to the loss.

"Any time you play Roger, there is always extra tension," said Pospisil. "I've always looked up to him so much. I was tense in the first set and that claimed a lot of energy.

"In the second I played better but in the third a couple of points made the difference."

Pospisil also pointed to his heavy playing schedule at Cincinnati as a problem.

"I had heavy legs at that point, maybe I was paying the price for the first set," he said. "I had five sets form singles and doubles the day before.

"I was missing some pop in my serve and he played well when he needed to."

Serena Williams advances

Elsewhere Wednesday, top-seeded Serena Williams won an opening match that was as close as it gets, rallying in both tiebreakers to move on.

Williams needed an hour and 54 minutes to beat Samantha Stosur 7-6 (7), 7-6 (7) on Wednesday, showing a little more poise on the toughest points.

"It's good when you play a lot of close matches and you come out on top — I'm defeated, I'm down and I come back and win," she said. "That's very good."

Most of the top players advanced, though not without a struggle.

Andy Murray took little more than an hour to beat Joao Sousa 6-3, 6-3. John Isner, who reached the finals last year, also advanced with a solid 6-3, 7-6 (1) victory over Marinko Matosevic.

Murray is still trying to get back into form from back surgery last September. He also made a break with coach Ivan Lendl in March that was a big adjustment.

"It's been a tough year," Murray said. "There have been a few things happen. Obviously coming back from surgery is hard. To me now, that isn't in any way an excuse. Now I have had enough time to get over it. Obviously with Ivan, that was also tough."

No. 4 Tomas Berdych converted only one break point while losing to Yen-Hsun Lu 3-6, 6-3, 6-4.

There was an upset in the women's draw. Third-seeded Petra Kvitova had trouble with her serve and lost to Elina Svitolina 6-2, 7-6 (2). Kvitova had nine double-faults and made just 52 per cent of her first serves.

With files from The Associated Press