MELBOURNE, Australia - 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 the shot was good, and left the call to the umpire.

“I’m proud of the way I fought,” said Murray, who had back surgery in September. “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 quarter finalist Grigor Dimitrov pushed a forehand just wide in a tiebreaker. Despite a painful blister on the palm of his left hand that hampered his serve, Nadal advanced 3-6, 7-6 (3), 7-6 (7), 6-2 against the 22-year-old Bulgarian.

“You lose a little bit of 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 consecutive Australian Open title with an upset victory in the quarterfinals and will face 2010 Wimbledon finalist Tomas Berdych in the semifinals today. Neither 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-yearold Canadian Eugenie Bouchard. Radwanska will face No. 20 Dominika Cibulkova, who convincingly beat No. 11 Simona Halep.

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 victory over Murray.

Nadal, who missed the 2013 Australian Open because of injury and had to watch as Murray beat Federer in the semifinals, came back strong last year. After missing seven months because of injury and illness, he won 10 titles - including majors at the French and U.S. Opens - and returned to the No. 1 ranking.

Meanwhile, Federer 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 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 victory 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.”

At a glance AUSTRALIAN OPEN Wednesday’s results At Melbourne Park Melbourne, Australia Purse: $29.72 million (Grand Slam) Surface: Hard-Outdoor SINGLES Men’s Quarterfinals Rafael Nadal (1), Spain, def. Grigor Dimitrov (22), Bulgaria, 3-6, 7-6 (3), 7-6 (7), 6-2.

Roger Federer (6), Switzerland, def. Andy Murray (4), Britain, 6-3, 6-4, 6-7 (6), 6-3.

Women Quarterfinals Dominika Cibulkova (20), Slovakia, def. Simona Halep (11), Romania, 6-3, 6-0.

Agnieszka Radwanska (5), Poland, def. Victoria Azarenka (2), Belarus, 6-1, 5-7, 6-0.

DOUBLES Men Quarterfinals Michael Llodra and Nicolas Mahut (13), France, def. Leander Paes, India, and Radek Stepanek (5), Czech Republic, 6-2, 7-6 (4).

Lukasz Kubot, Poland, and Robert Lindstedt (14), Sweden, def. Max Mirnyi, Belarus, and Mikhail Youzhny, Russia, 6-4, 5-7, 6-2.

Women Semifinals Ekaterina Makarova and Elena Vesnina (3), Russia, def. Raquel Kops-Jones and Abigail Spears (8), United States, 7-5, 3-6, 6-3.

Sara Errani and Roberta Vinci (1), Italy, def. Kveta Peschke, Czech Republic, and Katarina Srebotnik (4), Slovenia, 6-1, 6-4.

Mixed Quarterfinals Zheng Jie, China, and Scott Lipsky, United States, def. Anabel Medina Garrigues, Spain, and Bruno Soares (5), Brazil, 3-6, 6-4, 10-7.

Jarmila Gajdosova and Matthew Ebden, Australia, def. Katarina Srebotnik, Slovenia, and Rohan Bopanna (2), India, 7-5, 6-3.

Sports, Pages 20 on 01/23/2014