Roger not quite ready to roll over

Roger Federer blasted critics who say he's too old and insisted he will beat Novak Djokovic at a future Grand Slam after his four-set loss to the Serb in the Australian Open semifinals on Thursday.

Federer hasn't bested the runaway world No 1 at a major since the Wimbledon semifinals in 2012, when he last won a Grand Slam title. But when asked after Thursday's loss if he could ever again beat Djokovic again on the big stage, he bristled.

"Best-of-three, best-of-five, I can run for four or five hours. It's not a problem. I proved it in practice again in the offseason - no sweat. So from that standpoint I'm not worried about going into long rallies," Federer said.