World's former No. 1 tennis player Roger Federer kept getting asked during a long 2013 season in which he failed to reach the semifinals of a Grand Slam event for the first time in 11 years whether he was considering retirement.

The 2014 Australian Open is proving to be his answer as to why he isn't.

Federer, the No. 6 seed, has won four matches in Melbourne without losing a set and will take on No. 4 Andy Murray in the quarterfinals on Wednesday. He got there by routing 10th-seeded Jo-Wilfried Tsonga in straight sets during the fourth round.

And the Swiss star, who holds the record for most weeks at No. 1 in the world with 302, is full of confidence as he heads into his match against Murray, who is coming back from back surgery last fall.

"I don't have doubts anymore," Federer told the Daily Mirror. "For me, personally, I've overcome it. I know I'm going definitely in the right direction. This match against Tsonga was a big test for me. I don't need Murray to have a further test.

"What I've shown over the last three to four months to myself is that I'm more confident, that I know I'm most likely going to play OK in my next match, which wasn't always the case midway through last year, when I didn't know how I was going to feel during the match."

Murray beat Federer in five sets at last year's Australian Open, but Federer's last Grand Slam championship came in the 2012 Wimbledon final against Murray. The Scot owns an 11-9 career record over Federer.

Murray, who briefly lost his concentration against Stephane Robert in the fourth round and lost his first set of the match before rebounding with a four-set victory, is using last year's Australian Open result to lower Federer's spirits.

"Last year is pretty relevant because it's on the same court, and it will be under the same conditions," Murray said. "But, in an individual sport, any day is a new day. Anything can happen."