MELBOURNE: Former world number one Lleyton Hewitt admitted Monday he has no idea how to beat Roger Federer after the Swiss champion destroyed him for the 15th straight time.

Federer cruised through their Australian Open fourth round match 6-2, 6-3, 6-4 with Hewitt failing to beat his fellow 28-year-old in a streak stretching back to 2003.

The Australian two-time Grand Slam winner has taken just five sets off the current world number one in that time.

Hewitt said he felt like he was hitting the ball well against Federer and played good enough to beat most people, but was left clueless as to how to bridge the gap on one the greatest players the game has seen.

"From my point of view I did everything right," he said.

"I prepared exactly the way that I wanted to prepare for the Australian summer and I gave 100 percent every time again.

"I ran into the best player right at the moment I would say. I'm not sure right at the moment (how to beat Federer).

"If I knew, I would still be out there."

Hewitt said he felt like there was nothing he could do to blunt Federer's game, such was his form.

"He played special tennis," he said. "He hit the ball extremely clean, and I just couldn't get into his service games, which made it tough.

"I felt like he was putting the ball on a dime every time.

"Everyone says it wasn't an absolutely great year for him last year and he still won two Grand Slams and lost in two finals in five sets in the other two.

"He's obviously the benchmark."

Hewitt said he was disappointed to bow out to Federer while players that he believes he can beat are still in the tournament, without saying who he meant.

"The way I hit the ball tonight, I still think I could have taken a lot of other guys still left in the draw," he said.

"That's probably a little bit more frustrating."

There had been rumours Hewitt was struggling with a recurrence of a hip problem, but he dismissed any injury talk.