Federer demolishes Del Potro, sets up Roddick SF

World number two Roger Federer set up an Australian Open semi-final showdown with American Andy Roddick after he demolished Argentine Juan Martin del Potro 6-3, 6-0, 6-0 in the quarter-finals on Tuesday.

Two days after Federer was surprisingly taken to five sets by Tomas Berdych, the 13-times Grand Slam winner wasted little time in thrashing the eighth seed in just 80 minutes.

The 20-year-old del Potro, considered to be one of the rising players of the game having won four tournaments last year and the Auckland event earlier this month, had no answer to the Swiss.

Such was Federer's dominance, del Potro won just eight points in the second set and six in the third as the 27-year-old Federer advanced to his 19th successive Grand Slam semi-final.

Novak Djokovic's defence of his Australian Open title ended prematurely on Tuesday when he was forced to retire from his quarter-final against Roddick after the third game of the fourth set.

Roddick was leading 6-7, 6-4, 6-2, 2-1 when a visibly distressed Djokovic said he could no longer continue.

The 21-year-old Serb had called a medical time out after the third game of the third set, when he had held serve to take a 2-1 lead, but looked exhausted when play resumed and lost the next five games.

Roddick held four break points in the first game of the fourth set and while Djokovic battled back to hold serve it may have sapped any semblance of energy he had left, as the seventh seed won the next game then broke him to love.

The third-seeded Djokovic then walked off court, consulted the doctor and told chair umpire Carlos Ramos of Portugal "no more," before he went to congratulate Roddick, who has now advanced to his fourth Melbourne Park semi-final.