Federer into US Open last eight as Fish pulls out

World number one Roger Federer received a walkover into the US Open quarter-finals Monday when Americas Mardy Fish withdrew from their last-16 match because of health worries.Five-time champion Federer will face either Czech sixth seed Tomad Berdych or Spanish 11th seed Nicolas Almagro for a place in the semi-finals.It will be the top seeds 38th Grand Slam quarter-final.I regret that I have to withdraw from the US Open for precautionary measures, Fish said. I was reluctant to do so, but am following medical advisement.I had a good summer and look forward to resuming my tournament schedule in the fall.Fish, 30, missed two months of the season earlier this year because of a heart problem.He was hospitalised after the Miami Masters in March when his heart rate increased to three times its normal resting rate.The American then underwent a procedure called a cardiac catheter ablation in Los Angeles on May 23 to correct faulty wiring in his heart.