The big-serving Croatian was the last man to defeat Federer on grass, in the first round at Wimbledon in 2002, and the Swiss will be aiming to avenge that defeat to extend his unbeaten streak on the slick surface to 46.

Australian Lleyton Hewitt will fancy his chances of reaching his third semi-final here when he takes on Australian Open runner-up Marcos Baghdatis.

Hewitt had been expected to meet twice runner-up Andy Roddick at this stage but the American's defeat last week has made the 2002 champion the favourite to reach Sunday's final from the bottom half of the draw.

Baghdatis beat Roddick's conqueror Andy Murray in the last 16, but the Cypriot is in unchartered territory, having never won a match on grass until last month.

Double French Open champion Rafael Nadal is another grasscourt novice but despite his obvious limitations on the green lawns, he is enjoying his best run at Wimbledon and should be able to overcome Finn Jarkko Nieminen and set up a tantalising semi-final against Hewitt.

Czech 14th seed Radek Stepanek will battle it out with doubles specialist Jonas Bjorkman for a possible last-four meeting with Federer.