08/01/2012 10:19 EDT | Updated 10/01/2012 05:12 EDT

Roger Federer reaches quarterfinals at Olympics by beating Denis Istomin 7-5, 6-3

WIMBLEDON, England - Roger Federer endured two rain delays and a shaky moment late in the first set Wednesday to reach the quarter-finals at the Olympics by beating Denis Istomin of Uzbekistan 7-5, 6-3.

Serving at 5-all in the first set, the No. 1-seeded Federer faced three break points and erased them all. He then broke Istomin's serve and was in control from there.

A fourth-time Olympian, Federer has yet to win an singles medal at the Olympics, although he and Swiss teammate Stanislas Wawrinka did win the doubles at Beijing in 2008. Federer is playing his first tournament since winning a record-equaling seventh Wimbledon title.