Roger Federer advanced via walkover to the 2012 U.S. Open quarterfinals following the withdrawal of American Mardy Fish on Monday. The No. 23 seed, Fish was scheduled to play the world's best player this afternoon at Flushing Meadows but won't continue on after a recurring heart issue arose following his Sunday victory.

Fish missed time on the courts in April before undergoing a heart procedure in May.

Moving forward, Federer will go head to head with No. 6 seed Tomas Berdych, who defeated Spain's Nicolas Almagro in sets of 7-6 (4), 6-4 and 6-1 on Monday. Berdych, a 26-year-old from the Czech Republic, used 17 aces to dispatch Almagro, the No. 11 seed in the tournament. Almagro also struggled with five double-faults on the afternoon.

It is Berdych's first appearance in a U.S. Open quarterfinal.

For more coverage of the 2012 U.S. Open, check out SB Nation's tennis hub. To keep up with the live scores, head over to the official website.