Defending champion Novak Djokovic dismissed concerns over his fitness after outlasting David Ferrer on Wednesday to set up an Australian Open semi-final showdown against Andy Murray.
The tenacious Spaniard pushed Djokovic hard, manoeuvring him all over the court, but the top seed stepped up his game when it mattered to win 6-4, 7-6 (7/4), 6-1 in 2hr 44min.
Djokovic caused a scare when he grimaced in pain, clutching his left hamstring, as Ferrer levelled at 2-2 in the second set. He looked tentative and uncomfortable before shrugging off the problem to win the set on a tiebreak.
"Luckily for me it wasn't something that stayed there for a long time. It was just a sudden pain. But, look, you could expect before coming to this match that it's going to be very physical," said Djokovic, 24.
"David makes you run, makes you play an extra shot, makes you earn your points. I think I was hitting the ball really well from the baseline."
And Djokovic, who also said he had struggled with his breathing in the run-up to the match, gave himself a clean bill of health for Friday's semi-final against Murray, a repeat of last year's final won by the Serb.
"I don't have any physical issues. I feel very fit and I feel mentally, as well, very fresh," he said.
"It's just today I found it very difficult after a long time to breathe because I felt the whole day my nose was closed a little bit. I just wasn't able to get enough oxygen. I needed more time, which I didn't have."
Djokovic said he employed various strategies to prepare for matches, including breathing exercises, without revealing details.
The world number one earned a crucial service break in the fifth game of the first set which proved enough for him to take the lead against the fifth seed, after nearly an hour full of punishing rallies.
Looking tired at the end of the first set, Djokovic produced a stunning blind, backhand winner at full stretch from the back of the court early in the second as he broke in the first game.
After a second set lasting 76 minutes, he stepped up a gear with Ferrer unable to keep up his earlier intensity.
"Already after a couple of games I was feeling it was going to be a long match," Djokovic said.
"There was a big mental advantage to getting two sets up," he said, adding that he had stepped up his aggression as the match wore on.