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.
Fish, 30, missed two months of the season earlier this year because of a heart problem.
Late on Sunday, American 20th seed Andy Roddick delayed his retirement by advancing to the fourth round with a 7-5, 7-6 (7/1), 4-6, 6-4 victory over Italy’s Fabio Fognini on Sunday. Roddick, the 2003 US Open winner who is set to retire at the end of this tournament, will play for a spot in the quarter-finals against 2009 winner Juan Martin Del Potro, the seventh seed from Argentina.
Meanwhile, Australian Davis Cup captain Pat Rafter lashed out at Bernard Tomic’s “disgraceful” performance. The Australian 19-year-old made a tame second-round exit losing to the retiring Roddick 3-6, 4-6, 0-6, prompting allegations from John McEnroe that he was not trying in the final set. Tomic was then involved in an angry exchange with reporters when was asked to respond to McEnroe’s claims.
Rafter said: “I threw out the big D word, disgraceful, to him yesterday. There’s no use sugar-coating something, he has to do the work, and I’m sick and tired of tip-toeing around it,” Rafter told Fox Sports yesterday. —