Novak Djokovic's Australian Open exit surprised Andy Murray, but the top seed says it does not change anything in his pursuit of a fourth grand slam title.

The six-time champion departed at the hands of Denis Istomin on Thursday, the Serbian unable to turn a 2-1 lead into victory.

Rafael Nadal called the result "an accident" for Djokovic and Murray agrees it is more a blip from his close rival than the start of a worrying decline.

"Yeah, obviously [I was] surprised," he told a media conference after his third round win over Sam Querrey.

"But compared with, like, most players, it's not been that bad really. Obviously I think for him the early loss at Wimbledon and here would be disappointing. He'd want to play his best in the majors.

"But he still won the Masters Series in Canada. He was in the final at the US Open. He was in the finals of the [ATP] Tour Finals. He beat four or five top-10 players in the Tour Finals. He won the tournament in Doha last week.

"He has played some really good stuff over the last six or seven months, too. It's just not been, you know, as consistent as what it was the three years before. But how anyone is expected to keep up that level for their whole career, it's just unreasonable to expect that of anyone.

"There's been, yeah, a couple of surprising results, for sure. But on the whole, it's not been that bad."

He added: "For me, it doesn't change anything unless I was to potentially reach the final, because I can't play Novak in the fourth round or in the third round. Don't worry about that really.

"Obviously, if you're to get to the final, then it has an effect. A lot of the times when I've been in the final here, I've played against him. Had some tough ones."