Roger Federer said that he would take on super-fit Briton Andy Murray "any day" over five sets after surviving a marathon match in the Australian Open fourth round.
The Swiss insisted he felt fresh as a daisy after his three-and-a-half-hour work-out against Tomas Berdych and could easily go the distance with Murray despite their six-year age gap.
"I don't know how fit Murray is. I'll take him on any day in a five-setter," Federer said.
"He's younger so he's probably not so experienced. In the end it becomes very mental, and I know that this is where my biggest strength always comes into play.
"That's why I'm always going to favour myself in a fifth set."
Federer, 27, who has lost his last four matches against Murray, has fought a low-key war of words with the Scot since arriving here.
The 13-time Grand Slam champion pointedly questioned Murray's status as bookies' favourite at the start of the tournament, prompting the Briton to point out "contradictions" in Federer's comments.
The two remain on course to meet in next Sunday's final in a rematch of the US Open title match, where Federer recorded his last win over the 21-year-old Scot.
Fourth seed Murray is seeking his maiden Grand Slam win here and Britain's first since 1936.
American Andy Roddick, meanwhile, was full of confidence after dismissing Spain's Tommy Robrero, a player against who he has dropped just one set in 10 matches.
"I don't know that I've had a bad day against him," said the seventh seed, whose quarter-final opponent on Tuesday will be defending champion Novak Djokovic.
Roddick, who says he has trimmed down by about seven kilograms after a gruelling off-season, has made the semi-finals three times at Melbourne Park in his seven previous visits but has yet to reach the final.
"So far so good. I get to play another day," said the 26-year-old.
"I've been in the tournament for nine days now and just trying to get a step further each time.
"I'm not going to think about it in two parts. It's a whole tournament. I just want to continue to stay alive each day."
