"It was only a few points here and there that made the difference and I definitely felt I was in there, it's just a little bit unfortunate and not really the result you want here."
In other matches on Wednesday,
set up a clash with Roger Federer after the American went through following Michael Llodra's retirement.
Speaking on Wednesday, Federer played down his recent injury problems.
"The back is OK," said the Swiss. "I still wish it was better, but it's not really handicapping me even when I'm playing."
And asked about how his recent announcement that he and girlfriend Mirka Vavrinec are expecting their first child this summer will affect his tennis, the 27-year-old said: "I think it's going to be more fun.
"I think it's going to motivate me and inspire me, seeing how the child grows and so forth.
"Mirka's dream and mine too was to one day maybe have the kid on the sidelines, seeing me play while I'm still active. There's a great possibility now and even more why I want to play for a long time."
Third seed Novak Djokovic will face
after the Canadian beat Philipp Kohlschreiber of Germany 6-4 7-6 (7-2).
beat India's Yuki Bhambri 6-4 6-3 and will face the in-form Andy Roddick next, while
enjoyed an impressive 6-2 6-2 win over Ernests Gulbis.
of Ukraine will take on Ana Ivanovic after she beat Romania's Sorana Cirstea 6-2 6-1, while Russian wild card
beat Bethanie Mattek-Sands 7-6 (7-1) 6-3 to earn a clash with fourth seed Elena Dementieva.
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