There was disappointment in the air for ousted world number one Andy Murray, who bemoaned his failure to convert opportunities during his shock fourth-round loss to unheralded German Mischa Zverev at the Australian Open.

Murray was expected to ease into the quarter-finals of the season's opening grand slam but Zverev had other ideas as the world number 50 claimed a sensational 7-5 5-7 6-2 6-4 win on Sunday.

A three-time major champion and five-time runner-up at Melbourne Park, Murray could not overcome Zverev's relentless serve-and-volley approach on Rod Laver Arena and while he broke five times, he dropped serve on eight occasions, as he failed to progress beyond the fourth round of the Australian Open for the first time since 2009.

Murray praised the unseeded 29-year-old, who was competing in the last 16 of a major for the first time, but the Olympic gold medallist cut a frustrated figure post-match as he followed Novak Djokovic through the exit door in the opening week.

"Right now I'm more disappointed for myself," Murray told reporters. "Obviously it's a tough one to lose.

"I wanted to go far in this event. It's the earliest I've lost here for, I don't know, a long time. So I'm disappointed right now.

"Credit to him. He came up with great, great shots and played a really, really good match. You always finish matches you lose with things you maybe could have done a bit better, but he played some really good stuff."

"It's the shots he was coming up with when he did come forward," added Murray, who only won 36 per cent of his second serves as Zverev capitalised.

"He came up with some great pickups, you know, reflex volleys especially at the end of the match when it was tight. That was tough because I was hitting some good shots, chasing some good balls down.

"Just wasn't meant to be. He served very well when he needed to, especially when he was behind in games. He deserved to win because he played great when he was down, and also in the important moments.

"I was kind of behind in the last couple of sets the whole way. But the first two sets, I had chances. I was up a break I think in both of them pretty early. Couldn't convert my opportunities."

Murray continued: "I had some opportunities at the end. I think the last two service games I had chances. Maybe three service games in the last set I had opportunities. Maybe missed a couple of balls that he had been making.

"But then he came back from all of the mistakes that he made, kept coming, kept coming up with great shots. There's not too much you can do about that. Sometimes you got to say, Well played.

"It was obviously disappointing to lose. But he did some good stuff out there."

Pressed on whether he missed a golden opportunity to finally win the Australian Open after the elimination of two-time defending champion Djokovic, Murray said: "I don't know. I mean, every year you come is a different chance, different opportunity.

"Even had I got through this match, [Kei] Nishikori or Roger [Federer] are waiting. Stan's [Wawrinka] still in. Guys like [Jo-Wilfried] Tsonga. I don't know exactly what's happening in the match with Dan [Evans], but you've got Roger plus three guys that are pretty much in the top 10 in the world in my half.

"There's certainly no guarantees, even if I got through match, that I would have gone further.

"It's disappointing to lose. I don't feel like this is any more of an opportunity than other years."