Rightly or wrongly, it seemed to spark his resurgence, breaking Federer when the 17-time major winner was serving for the match in the 10th game, and then pushing it to a fourth set when he won six of the last seven points in the tiebreaker.
"They showed it twice on the replay," Federer said of the bounce. "It's an umpire's call. It looked good."
After spending three months off the circuit following minor back surgery, Murray appeared to be in discomfort at times in the match, clutching at his lower back.
"I was proud of the way I fought," Murray said. "That's the highest level I've played at in a long time. My serve slowed down a bit in the fourth set, especially the first couple points when I was getting up after the change of ends."
After Federer won the opening game of the fourth set, the two played a 10-deuce game in which Murray saved six break points before Murray leveled. But Federer finally broke Murray in the eighth game then held serve to win the match in 3 hours, 20 minutes.
"I'm back," Federer said. "It was a great game on many levels, not just physically ... but mentally, also."
In the earlier match on Rod Laver Arena, Nadal received treatment several times for a nasty-looking blister on the palm of his left hand that he said caused him to serve slower than usual. He fended off three set points in the third, including two in the tiebreaker, and won on his first set point.
