Defending champion Roger Federer made short work of the tallest man in tennis at Wimbledon on Monday, winning his fourth round match against Croatian Ivo Karlovic 6-3, 7-6, 7-6.

The 6ft 10ins (2.08m) ace machine from Zagreb knocked out Lleyton Hewitt when the Australian was defending champion last year but there was never any danger of Federer going the same way on court one.

Karlovic had racked up 95 aces in three rounds going into the match but Federer had not lost his serve once and it was the Croat who cracked first at 2-3 in the opening set.

The peerless Swiss actually had to save two break points in the next game but quickly recovered to take the set and won the next two on tiebreak 7-3 and 7-5 respectively.

Federer faces Hewitt or Spaniard Carlos Moya for a place in the semi-finals.

Russian 13th seed Maria Sharapova reached her second Grand Slam quarter-final with a gritty 6-4 7-5 victory over American Amy Frazier in the fourth round.

The determined 17-year-old, who made the last eight of the French Open a month ago, trailed for much of the first set to 31-year-old Frazier but raised her game to break conclusively at 5-4.

Frazier made Sharapova fight to hold serve throughout but the rangy Russian's bludgeoning power secured her a fourth successive straight sets victory.

Sharapova, who reached the fourth round on her Wimbledon debut last year, will play either Thailand's Tamarine Tanasugarn or Ai Sugiyama of Japan in the last eight.