MELBOURNE, Australia (AP) -- On the eve of the Australian Open, Novak Djokovic was asked if he had noticed anything different about Andy Murray.
"He has a shorter haircut," said the five-time Grand Slam winner, smiling.
But the top-ranked Djokovic then turned serious because Murray's makeover is no joking matter.
The 25-year-old player from Scotland is attempting to win a second consecutive Grand Slam after a breakthrough year that included wins at the London Olympics and the U.S. Open. He arrived in Melbourne with a new demeanor, a sense of calm and confidence.
"I think mentally something switched in his head," Djokovic said. "And he just started believing much more in his abilities.
"Now that he's done it, he's definitely right up there, one of the first few favorites for any tournament he plays."
The third-seeded Murray advanced to the semifinals Wednesday, grabbing a spot in an all-star lineup featuring the top four players.
Djokovic is in the first semifinal against No. 4 David Ferrer, who took the spot in the absence of an injured Rafael Nadal.
Third-seeded Murray faces No. 2 Roger Federer in the latest rematch in a tight rivalry. Murray leads Federer 10-9 in the series, including last year's Olympic final. But he has played the Swiss star in three Grand Slam finals and lost them all.
"I'm expecting a tough match," said Federer, describing Murray as clever and tactical. "He's changed his game around a bit. He's playing more defensive. I'm looking forward to it."
Federer is aiming for his 18th Grand Slam. The Swiss star stamped his authority on center court by beating the athletic Jo-Wilfried Tsonga 7-6 (4), 4-6, 7-6 (4), 3-6, 6-3 to reach the Australian Open semifinals for a 10th consecutive year.
After losing, Tsonga picked his favorite to win the tournament: "I would say Andy, for the moment. But it could change, of course."
Murray won his quarterfinal against Jeremy Chardy of France 6-4, 6-1, 6-2 to extend a streak of straight-set wins into the semis. Of all the men in the draw, Murray is technically the freshest, having spent less time on court -- just under nine hours in the past 10 days.
Chardy walked into his post-match news conference saying he couldn't believe how well Murray had played.
"I've played him several times, and every time I always thought I had a chance," said the 36th-ranked Frenchman, who beat Murray in August in Cincinnati. "Today, he never let me think even once I had a chance to win.
"He's calm on the court. He was so concentrated, and had so much intensity from the start. Right away, I was in difficulty. And during the whole match, he never dropped his level."
Murray's intensity on court diminishes only slightly in his news conferences where he is modest, polite and mild-mannered. He said he was pleased to reach the 12th Grand Slam semifinal of his career.
"I thought I did a pretty good job throughout the match," he said. "I can't be disappointed about being in the semis of a slam without dropping a set. That would be silly."
Murray reached the Australian Open semifinals last year, losing to Djokovic. He has made the Melbourne finals on two occasions, losing to Djokovic in 2011 and Federer in 2010.
Before arriving in Melbourne last year, Murray teamed up with tennis great Ivan Lendl. His coaching has helped produce a new aggressiveness and willingness to take chances on court.
Under Lendl's tutelage, Murray made his breakthrough.
He became the first man to win at the Olympics and U.S. Open in the same year. His win at Flushing Meadows made him the first British man in 76 years to win a Grand Slam -- and lifted an enormous burden.
"I kind of maybe always felt like I was having to prove something every time I went on court because I hadn't won a slam," Murray said before the tournament started. "It's nice to not have to worry about that anymore."
After his Wednesday quarterfinal, Murray dismissed comments in the British media that he was upset by having to play all day matches in the hot sun while Federer was given cooler night slots during prime-time viewing hours on center court.
"I have no complaints about the schedule at all, and I didn't complain about it the other day," Murray said. "Sometimes it works in your favor and sometimes it doesn't."
The Federer-Tsonga quarterfinal was held Wednesday night at a packed Rod Laver Arena. But instead of studying his next opponent, Murray said he planned to practice at a nearby court.
"Rather than going and watching this match, I'll go out and hit some balls under the lights to be as best prepared as possible," he said.
Asked if he felt prepared to go against his old rivals, Murray replied: "Hopefully, I will go into the matches a little bit calmer than usual or then I have in the past."