Novak Djokovic refused to entertain questions about a potential Australian Open final against Rafael Nadal after sealing his spot in the last four when Kei Nishikori retired due to injury.

Djokovic will face first-time grand slam semifinalist Lucas Pouille, having spent only 52 minutes on Rod Laver Arena before Nishikori quit due to an issue with his right quad on Wednesday.

Nadal comes up against Stefanos Tsitsipas in the other semi-final, with the expectation that the top two players in the rankings will compete for the title at Melbourne Park on Sunday.

World number one Djokovic, aiming to become the first man to win the tournament seven times, was in no mood to discuss the possibility of a mouth-watering showdown with Nadal after staying on course to make history.

The top seed replied when asked if he was prepared to face the Spaniard: "Right now it's my press conference, so it will be nice to talk about me more than Nadal.

"If you want to talk about our possible encounter, we talk about that if we both win semis."

Djokovic expressed his sympathy for Nishikori, who came through three five-set contests to reach the last eight.

The 14-time grand slam champion said: "I'm really sorry to see him go through pain. He's had some tough injuries in the last couple of years. I'm sure he's not feeling great about ending the grand slam this way.

"But he's had some marathon matches this tournament that probably have taken the toll on his body."