By Alastair Himmer

MELBOURNE (Reuters) - Roger Federer reacted with disdain when asked if Thursday's Australian Open semi-final defeat by Serbia's Novak Djokovic signaled the end of an era in men's tennis.

Federer, however, bristled when it was suggested the absence of the world's top two represented a passing of the baton after his 7-6 7-5 6-4 ambushing by Djokovic in Melbourne.

"Yeah, I mean they say that very quickly," snapped the Swiss maestro, winner of a record 16 grand slam crowns. "Let's talk again in six months!"

Djokovic, at the 2008 Australian Open, and Argentine Juan Martin del Potro, at the 2009 U.S. Open, are the only other men to have won any of the big four in the 'Roger-Rafa' era.

The 29-year-old Federer insisted he was far from done.

"I'm very optimistic about the next 15 tournaments, or however many I'm playing.

"I've barely lost matches lately," added the former world number one, who has seen a marked improvement in his form since teaming up with Pete Sampras's old coach Paul Annacone after ditching out of Wimbledon in the quarter-finals last July.

"So I'm happy with where my game is at, with where my condition is at. I'm really excited for what's to come. This is obviously a bit of a blow.

"At the same time, I played a good tournament. I have no regrets. I left everything out there. We'll see what comes next."

Federer, unusually rattled by noise from Djokovic's entourage and the Serb's incessant ball bouncing between serves, put his defeat down to an off night.

"Novak played a great game," shrugged Federer. "I just ran into a player who was a bit better than me tonight. I can move on from this with a good mindset, to be honest.

"That's what's important right now, that I don't feel like I have physical issues or I'm not playing the right way. It was just a few points here and there."

(Editing by Martyn Herman)