Australian Open 2014: Victory in Melbourne would be Roger Federer's 'biggest triumph', claims Martina Navratilova

Andy Murray could also rank the achievement among his greatest triumphs due to the difficult draw

Roger Federer is in his best form since his 2012 Wimbledon success, claims Greg Rusedski (GETTY IMAGES)

Winning the Australian Open would represent that greatest achievement of Roger Federer's career, according to Martina Navratilova.

Federer had not really been talked about as a potential champion until his crushing fourth-round win over Jo-Wilfried Tsonga.

The old magic appeared to be back in the new Federer racquet and on Wednesday he will meet Andy Murray in the quarter-finals under the lights on Rod Laver Arena.

Should he get through that one, Rafael Nadal would probably await, although at least Novak Djokovic is no longer in the way after Stanislas Wawrinka's sensational upset.

Navratilova said: "It's anybody's ball game. Roger Federer to me has the toughest draw of anybody. He had the easiest draw getting to the round of 16, now he has the toughest draw.

"If he were to win this tournament, to me it would be his biggest triumph, and the same could be said of Andy Murray."

Federer is not usually a man short on confidence, and the doubts he talked so candidly about during his 2013 struggles have disappeared, for the moment at least.

He knows trying to beat Tsonga, Murray and Nadal back to back is an extremely tough ask, but one he will relish.

Federer said: "You need to be able to come through some matches quickly. It's a tough thing to do. Clearly you need to change your game depending on the players.

"You are always also a bit dependent on how good their form is, how good is yours. Can you do it three or four times in a row.

"It's definitely a tough task. Then again, if you don't embrace that challenge, you might as well not enter the draw. You might as well stay at home and watch other guys battle it out.

"That's what I like. I like playing the best. And you need to take it to them. You need to play aggressive against the top guys, me included. You don't want to wait for stuff to happen. I think that usually is good for success."

As well as his bigger-headed racquet, Federer also has a new man in his corner in Stefan Edberg.

The Swede has agreed to work with Federer for a minimum of 10 weeks this year, and the Swiss hopes that can help him against Murray, whom he lost to in the semi-finals in Melbourne 12 months ago.

Murray is coached by Edberg's former 1980s rival Ivan Lendl, and Federer said: "It's not going to hurt. It could be very helpful. It's just a different perspective.

"He did things his way back in the day. I'm sure things were different back then. But still you can take so many things from his experience.

"I want to maybe try out a few things that worked for him, try out a few things that he thinks would work out for me this time around.

"We'll discuss it, assess it, but he's here now more for just support, making me feel comfortable, giving me the right advice, pre-match, post-match, discussing it with Severin (Luthi), my coach.

"We're still going through the motions a little bit here. We're still trying to get a feel for how we want it to be exactly.

"How much should we talk? How much is too much? He's doing really a nice job, and he was happy with my performance (against Tsonga), which makes me clearly very happy, too."

PA