Combo photo shows James Blake of the US (L) celebrates winning a men's singles quarterfinal tennis match against Roger Federer of Switzerland and Roger Federer of Switzerland waves goodbye August 14, 2008. [Agencies]

BEIJING -- Top seed Roger Federer and American Williams sisters were all sent packing in the quarterfinals of the Beijing Olympic tennis event on Thursday.

The heavy rain had delayed the competition for almost four hours and then came back to hit the schedule again after midnight when three matches were still going on.

Federer became the largest seed casualty of the day as the Swiss world number one lost to American eighth seed James Blake in the men's singles quarterfinals.

Federer was playing below standard, slumping at 6-4, 7-6 (7-2) in just one hour and 30 minutes.

"I'm speechless. This is unbelievable. It's not very often you get to say you beat the No. 1 player in the world anytime, but to do it at the Olympics with USA on your chest, I'm so proud to be a part of this team,"  said Blake.

It was the American's first win over the Swiss. Federer entered the match with an 8-0 record in matches against his opponent and had only ever lost one set to Blake.