Andy Murray's hopes of finally getting his hands on the Australian Open title were ended for another year when the top seed and world No 1 was tied up in knots and flung out of the fourth round by Germany's Mischa Zverev on Sunday.

With reigning champ Novak Djokovic having been knocked out in the second round, a Grand Slam will head into the second week without its top two men's seeds for the first time since the 2004 French Open.

Zverev, in the fourth round at a Grand Slam for the first time after a career ravaged by injury, flummoxed Murray with his unorthodox serve-volley game and broke the Wimbledon and Olympic champion eight times.

The world No 50 was helped by a below-par performance from Murray, but thoroughly deserved his 7-5, 5-7, 6-2, 6-4 victory over three and a half hours at Rod Laver Arena, which earned him a quarterfinal meeting with No 17 seed Roger Federer, who defeated No 5 seed Kei Nishikori of Japan, 6-7 (4), 6-4- 6-1, 4-6, 6-3.

"He deserved to win because he played great when he was down and also in the important moments," said Britain's Murray.

"He kept coming up with great shots; there's not too much you can do about that. Sometimes you've got to say, 'Well played!' It was obviously disappointing to lose. But he did some good stuff out there."

Murray prides himself on the variety of weapons at his disposal but some, like his lob, deserted him while others were undermined by the lack of pace Zverev offered him to work with.

Zverev served solidly and came up with 52 winners, charging the net 118 times and breaking Murray five times in the first two sets alone.

"Honestly, I was in a little coma, just serving and volleying my way through," said Zverev.

"There were some points I don't know how I won, but somehow I made it."

There were some nerves as Zverev served for the match - he netted one straight - forward overhead - but he recovered his composure to go through to the quarterfinals when Murray blasted a forehand long.

"I got excited," Zverev said. "It was easy to stay aggressive but it was definitely tough to stay calm ... I was surprised at how I managed to get so many first serves in.

"It means the world to me and it means a lot that my family is here and my box is full."

Zverev sat in the same box on Saturday, watching his 19-year-old brother Alexander, tipped by many to be a future Grand Slam champion, lose over five sets to Rafa Nadal.

It will now be the 29-year-old older sibling, who will take the family name into the final week of a Grand Slam for the first time.

Murray, who has lost five finals at Melbourne Park, four of them to Djokovic, said he will be back.

"I've had tough losses in my career in the past," he said. "I've come back from them. This is a tough one, but I'm sure I'll be able to bounce back from it."

Murray was coming off a magnificent 2016 that included a second Wimbledon crown, a successful Olympic title defense at the Rio de Janeiro Games and replacing Djokovic as world No 1 for the first time.

"I'm obviously down about it. It's just tennis. I've had great success for a number of months," he said.

"Obviously in the biggest events you want to do your best. That's not been the case here. You know, it happens."

Murray had not lost before the quarterfinals at the Australian Open since going out to Spaniard Fernando Verdasco in five sets in 2009.

He had also not lost to a player ranked as low as the Zverev in Melbourne since he fell to No 51 Juan Ignacio Chela in 2006.