Roger Federer chases down a ball. Federer beat Austria's Jurgen Melzer during the fourth round of the U.S. Open on Monday, Sept. 6 in New York.

Jurgen Melzer hits a return to Roger Federer. Melzer gave it a run, but lost to Federer in straight sets.

Roger Federer returns a shot. Federer advanced to the quarterfinals of the U.S. Open with his win.

Vera Zvonareva hits a return to Andrea Petkovic. Zvonareva's 6-1, 6-2 win advanced her to the U.S. Open quarterfinals.

Andrea Petkovic comes to the net. Petkovic couldn't get her game going in a loss to Vera Zvonareva.

Vera Zvonareva braces herself after slipping against Andrea Petkovic. Zvonareva won the match.

Danish tennis player Caroline Wozniacki celebrates after winning against Russian player Maria Sharapova during Day 8 of the 2010 U.S. Open. Wozniacki won 6-3, 6-4.

No. 14 seeded Maria Sharapova returns to No. 1 seeded Caroline Wozniacki. Sharapova couldn't overcome her 36 unforced errors. Wozniacki only registered 10.

Wozniacki returns a shot to Sharapova. Wozniacki only had 16 winners on the day, but she also only had 10 unforced errors.

Maria Sharapova stands on the court during play against Caroline Wozniacki. Sharapova didn't help her cause much with nine double faults.

No. 19 Mardy Fish of the United States reacts after breaking Novak Djokovic of Serbia. It was a rare high point for Fish during the match, though, as Djokovic won in straight sets, 6-3, 6-4, 6-1.

Novak Djokovic had been coming up with more double faults than aces as of late, but his serving game looked better against Mardy Fish. He had five aces and four double faults on the day.

Mardy Fish of the United States returns a shot against Novak Djokovic of Serbia. Fish was only able to rack up 13 winners in the match, while Djokovic tallied 30.

Dominika Cibulkova of Slovakia celebrates after defeating No. 11 Svetlana Kuznetsova of Russia. Cibulkova pulled off the big upset, winning 7-5, 7-6 (7-5).

No. 11 Svetlana Kuznetsova of Russia returns a shot against Dominika Cibulkova of Slovakia. Kuznetsova was the heavy favorite, but 42 unforced errors led to her demise.

Dominika Cibulkova of Slovakia returns a shot against Svetlana Kuznetsova. While Kuznetsova tallied 42 unforced errors and 10 double faults, Cibulkova gave less points away with 25 unforced errors and four double faults.

Gael Monfils of France returns a shot against fellow countryman Richard Gasquet during their fourth round match. Monfil won in straight sets, 6-4, 7-5, 7-5.

Richard Gasquet of France returns a shot to Gael Monfils. Gasquet tallied 39 winners, but he also registered 40 unforced errors in the loss.

Gael Monfils of France after winning against Richard Gasquet during the fourth round of the U.S. Open.

Venus Williams smiles after autographing her book 'Come to Win' for a fan during Day 8 of the U.S. Open. Francesca Schiavone awaits Venus in her next match.