Teenager stuns Sharapova as Federer holds on

Maria Sharapova's troubled year reached its lowest point here yesterday when the defending champion was knocked out of the third round of the US Open by Agnieszka Radwanska, an 18-year-old Pole. Making her earliest exit from a Grand Slam tournament for three years, Sharapova lost 6-4 1-6 6-2 to become the first women's No 2 seed to lose at this stage of the tournament since 1981.

Sharapova served 12 double faults and made 49 unforced errors. The Russian had trouble with the breezy conditions, but she also seemed to pay a price for the shoulder problems which have bothered her all year. Sharapova won eight successive games to lead 2-0 in the final set, but a double fault gave Radwanska a crucial break to lead 3-2 as the Pole won six games in a row to take the match.

Radwanska, whose younger sister Urszula is the Wimbledon junior champion, won that title herself two years ago and has made rapid progress this year. She played with great confidence and attacked Sharapova's second serve mercilessly, standing several feet inside the baseline. "I knew she hates it if somebody moves when she's serving," Radwanska said. " She made so many errors on her second serve."

The world No 32 said she would celebrate by buying expensive designer handbags for herself and her sister. Sharapova refused to offer any excuse, saying her shoulder was "fine".

Roger Federer survived an early wobble before beating John Isner, the 6ft 9in American who has been blasting opponents off the court this summer, 6-7 6-2 6-4 6-2. Isner is only the fourth player, after Rafael Nadal, Juan Carlos Ferrero and Tommy Robredo, to take a set off Federer in a Grand Slam this year.