Defending U.S. Open tennis champion and second seed Maria Sharapova of Russia has become the first big upset of this year's tournament in New York.
Polish teenager Agnieszka Radwanska shocked Sharapova, 6-4, 1-6, 6-2.
Another seeded Russian also fell in third-round play Saturday when unseeded Agnes Szavay of Hungary downed number seven Nadia Petrova (6-4, 6-4).
Other seeded women ousted Saturday include two Swiss players: number 11 Patty Schnyder and number 16 Martina Hingis.
The highest seeds advancing were two Russians - number four Svetlana Kuznetsova, and sixth seed Anna Chakvetadze.
On the men's side, defending champion and top seed Roger Federer of Switzerland dropped the first set to American rookie John Isner, then breezed on to the fourth round with a 6-7, 6-2, 6-4, 6-2 victory. Federer is on course for his fourth straight U.S. Open title.
Other top-10 seeds advancing were number four Nikolay Davydenko of Russia, number five Andy Roddick of the United States, sixth seed James Blake of the United States, number nine Tomas Berdych of the Czech Republic, and 10th seed Tommy Haas of Germany.
Unseeded Lee Hyung-taik of South Korean advanced to the fourth round by unseeded number 19 Andy Murray of Britain, 6-3, 6-3, 2-6, 7-5.
Some information for this report was provided by AFP, AP and Reuters.