MELBOURNE, Australia (AP) -- For a full two sets and nine games, Roger Federer was the picture of poise, picking up half-volleys with vintage panache and placing winners past Andy Murray.
Then, in the bounce of a ball - or two bounces of the ball, depending on opinion - the 17-time major winner was transformed back into the vulnerable, 2013-edition Federer.
After breaking Murray to get a chance to serve for the match on Wednesday and a spot in the Australian Open semifinals for an 11th consecutive year, Federer dropped serve.
He recovered and jumped to a 5-2 lead in the tiebreaker, but then Murray rallied and won six of the last seven points to prolong the quarterfinal.
After wasting a handful of break-point chances in Murray's next service game, which lasted almost 19 minutes, Federer finally wore down the Wimbledon champion 6-3, 6-4, 6-7 (6), 6-3 to set up a semifinal showdown with top-ranked Rafael Nadal.
''For me it was just a matter of staying calm and forgetting about it a little bit because, you know, the match was great until that point,'' Federer said.
Murray made his resurgence after disputing a point in the ninth game of the third set, when he thought the ball had bounced twice before Federer hit it. Replays shown in Rod Laver Arena were inconclusive. Federer thought was good, and left the call to the umpire.
''I'm proud of the way I fought,'' Murray said. ''I've come a long way in four months.''
Nadal lost the first set and faced set points in the third, getting a reprieve when first-time quarterfinalist Grigor Dimitrov pushed a forehand just wide in a tiebreaker. Despite painful blisters on his left hand that hampered his serve, Nadal advanced 3-6, 7-6 (3), 7-6 (7), 6-2 of the 22-year-old Bulgarian.
''You lose a little bit the coordination. Yeah, that's a big deal,'' Nadal said of his grip. ''I served slower. I served bad (but) I was able to win a match against a very difficult opponent, so that has much more value than when everything is great.
''And because of these victories, sometimes happens that next day you are able to play much better - and these victories are more important than the days that you are playing great.''
And that's how the greatest of modern day champions reconcile it. On a day when two-time defending Australian Open champion Victoria Azarenka lost 6-1, 5-7, 6-0 to No. 5 Agnieszka Radwanska and following other stars out of the tournament, Nadal and Federer won back-to-back matches on center court to set up their 33rd showdown.
Stan Wawrinka ended Novak Djokovic's bid for a fourth straight Australian Open title with an upset win in the quarterfinals and will face 2010 Wimbledon finalist Tomas Berdych in the semifinals on Thursday. Neither of them has won a Grand Slam title, but one is guaranteed to get a chance in Australia.
That match will be preceded by the women's semifinals. Li Na, the 2011 French Open champion and a two-time Australian Open finalist, is the only major winner left the draw. She'll take on 19-year-old Canadian Eugenie Bouchard. Radwanska will faces No. 20 Dominika Cibulkova, who beat No. 11 Simona Halep convincingly.
Nadal and Federer aren't back in action until Friday. It gives Nadal time for his blisters to heal, and Federer time to recover from his tight win over Murray, who came into the Australian Open after spending most of the last three months recovering from a minor back operation.
Nadal, who missed the 2013 Australian Open through injury and had to watch as Murray beat Federer in the semifinals, came back as strong as ever last year. After missing seven months through injury and illness, he won 10 titles - including majors at the French and U.S. Opens - and returned to the No. 1 ranking.
Federer, meanwhile, had his worst year in 11, failing to make any of the Grand Slam finals and dropping to No. 6 in the rankings as he struggled with muscle injuries and came to terms with a new, bigger racket.
After recruiting six-time major winner Stefan Edberg as a coach, and adjusting to the new racket, he's finally feeling capable of winning a major again.
He believes the win over Murray demonstrated that.
''I definitely think that's what I used to do so well, the transition game from defense to offense,'' Federer said. ''I definitely sensed that today. I am back.''