Novak Djokovic says he is facing the greatest injury challenge of his grand slam career after securing a place in his ninth Australian Open semi-final.
The world No.1 survived a gruelling slugfest against German Alexander Zverev to win their quarter-final 6-7 (8-6) 6-2 6-4 7-6 (8-6).
The eight-time Open champion recovered from breaks down in the third and fourth sets to conquer sixth-seeded Zverev in a high-quality match lasting three-and-a-half hours at Melbourne Park.
He will now meet Russian qualifier Aslan Karatsev, who is making a fairytale run on his grand slam debut, in a David and Goliath final-four match-up.
Djokovic has not been training in between matches as he attempts to recover from an abdominal strain.
"I have had a rollercoaster tournament," the 33-year-old said.
"I have never experienced this kind of injury during a grand slam and (been able to) keep going.
"The positive thing is that I actually felt the best from the beginning of the second set until the end of the match that I have since when the injury happened."
Djokovic often became frustrated during the contest, which finished in the early hours of Wednesday morning.
In a fiery moment, Djokovic destroyed a racquet after failing to return a speedy Zverev serve when down in the third set, earning him a code violation.
He eventually dropped the game to fall behind 4-1 but the release of frustration sparked Djokovic's comeback to claim the set.
"It was a relief for me, but I wouldn't recommend this kind of relief channelling," Djokovic said.
"I'm not proud of these kind of moments....I have my own demons that I have to fight with, and I'm sure everybody else has them too."
Since demolishing Jeremy Chardy in the first-round, Djokovic has spent more than 12 hours on court as he chases his 18th major title, which would put him just two behind Roger Federer's record.
In an ominous sign for his rivals, including world No.2 Rafael Nadal, Djokovic has won the first major of the year every time he has qualified for the semi-finals.
The result continues Zverev's drought of having never defeated a top-10 opponent at a grand slam.
The 23-year-old had a set-point in the fourth, but was unable to take the match into a deciding set as Djokovic pulled off a remarkable victory.
"Down to the last very last shot, it was anyone's game," Djokovic said.
"A lot of nerves out there, a lot of pressure and emotionally I feel a little bit drained. It was a great battle."
Djokovic will fly blind into the contest with Karatsev as he had never seen the world No.114 play before this tournament.
