Tennis: Federer lets rival know of the tough task ahead

Novak Djokovic is full of belief but, with typical Swiss subtlety, Roger Federer has cautioned the Serb against believing he has the defending champion's number heading into their Australian Open semifinal tonight.

A fighting five-set US Open semifinal triumph and his straight-sets defeat of the 16-times major champion in the 2008 Melbourne Park semifinals are among six Djokovic wins from 19 career encounters.

Throw in Djokovic's Davis Cup final heroics last month in Belgrade and the world No 3 is high on confidence - in the form of his life, as he put it - ahead of episode 20 of their rivalry.

"I always try to win against him. No question about that," Djokovic said after crushing Wimbledon runner-up Tomas Berdych 6-1, 7-6 (7-5), 6-1 in the quarter-finals.

"I've won against him in different occasions, mostly on the hardcourts. So this is the chance that I can use.

"Definitely you have to start well. You have to try to get him on the run as much as you can and try to let him know you're there to win."

Federer gently reminded Djokovic the Serb's two biggest wins over him came with qualifiers.

"The US Open was a close match," Federer said after extending his winning streak to 15 with his devastating 6-1, 6-3, 6-3 quarter-final dispatch of countryman Stanislas Wawrinka.

"I had two match points ... I guess I should have won really. I mean, I was playing good enough to win.

"But I was a bit confused mentally maybe because we played the second session - it was a back-to-back with the Super Saturday [in New York], which I'm not a huge fan of.

"Maybe I just felt like I have to get out of this match as quick as I could to save energy to play Rafa [Nadal] the next day. I think it ended up hurting me losing the match at the end.

"It was unfortunate. Novak and myself both played a good match. In the end, it was a shot here and there."

Federer's 2008 Australian Open semifinal disclaimer came in the form of glandular fever, or mononucleosis.

"I had mono," the four-time champion said of his only loss in Melbourne to anyone other than Nadal in six years. But while Federer regained his supremacy over Djokovic with back-to-back victories in Basel and London last year, the Serb insists he arrived at the season-opening grand slam at the peak of his powers: "I'm starting to play my best tennis in last five, six months. I have more experience on the court," he said.

- AAP