Fourth seed Stan Wawrinka denied there is additional pressure on him to win the Australian Open, despite Andy Murray following Novak Djokovic out of the grand slam.

Murray was stunned by unseeded Mischa Zverev on Sunday, the German claiming a remarkable 7-5 5-7 6-2 6-4 fourth-round victory in Melbourne.

Zverev's progression to the quarter-finals means the Australian Open will be without the world number one and defending champion Novak Djokovic for the second week, after the latter was upstaged by Denis Istomin in round two.

It opens up the draw for players like 2014 champion Wawrinka, who overcame Andreas Seppi 7-6 (7-2) 7-6 (7-4) 7-6 (7-4), but the three-time major champion is refusing to look too far ahead.

"I don't know why I should feel more pressure," Wawrinka said. "I'm just in quarter-final.

"It's big surprise that they not in the draw anymore, but my next match is the quarter-final. I'm not thinking about semi or final that I will not have to play Andy or Novak. That's the last thing in my head.

"So far I have a big match in quarter-final. It's for sure opening the draw on the other side with Novak not here. It's going to be interesting to see who is going to get there. But you have some big players there. You have [Rafael] Nadal. Roger [Federer] is playing now against [Kei] Nishikori.

"I just think it's interesting tournament."

Of Murray's four-set loss on Rod Laver Arena, the Brit failing to advance beyond the fourth round of the Australian Open for the first time since 2009, Wawrinka added: "It's a big surprise for sure.

"It shows that it's not so easy as we can think, or when we see the draw, to just win, keep winning all the time.

"He's number one in the world. He's been amazing last year, especially the way he finished the year by winning every tournament he was playing.

"But still, every match you have to enter the court, you have to fight. You play against some really strong player. It's tough to just win or be in the final in every tournament for any player."