ANDY Murray believes the decline of Novak Djokovic has been exaggerated and insists the Serb is just a victim of his own success.

Murray beat Sam Querrey to move into the Australian Open fourth round on Friday, less than 24 hours after Djokovic had crashed out to wildcard Denis Istomin.

Djokovic’s exit leaves Murray in pole position to claim his first title in Melbourne and continues the 29-year-old Serb’s dip in form since winning his fourth grand slam in-a-row at the French Open last year.

A third-round defeat at Wimbledon, to Querrey, was followed by a first round loss at the Olympics. Djokovic reached the final at the US Open in September but was outplayed by Stan Wawrinka. Asked why he thought Djokovic was struggling, Murray said: “I mean, struggling by the highest standards. But compared with 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 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 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 a couple of surprising results, for sure, but on the whole, it’s not been that bad.”

Murray will play Germany’s Mischa Zverev on Sunday and is now heavy favourite to win the Australian Open given he has reached the final here five times and four times lost to Djokovic. But the Scot insists he is not feeling any extra pressure as a result of his rival’s defeat.

“Obviously I was surprised. Novak’s record here speaks for itself. He’s had incredible success here over the years,” Murray said.

“But 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. I don’t worry about that really. Obviously, if you 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 and had some tough ones.

“I wasn’t scheduled to play Novak today so my job’s to concentrate on Sam and to go into that match with a clear head and a good game plan and try to play well. I did that.”

Murray’s 6-4 6-2 6-4 win over Querrey came with little complication as the world No 1’s speed and precision proved too strong for the American’s big-hitting game.

The match turned at 4-4 in the opening set, when Murray unleashed a series of stupendous groundstrokes to break and then served out the opening set. “I thought I did pretty good today,” Murray said. “The start of the match was hard. Sam came out serving big. He was really going for his shots.

“The end of that first set was important. He had a breakpoint at 4-3. When I saved that and broke the next game, momentum was with me.”

Murray rolled over on his right ankle during his win over Andrey Rublev on Wednesday but said the injury had not caused him any major discomfort.

“It feels really good,” Murray said. “It was sore yesterday and a little bit stiff this morning but it feels good.

“After the first few games, where I was maybe slightly hesitant, I moved really well towards the end of the first, second and third set. So that was really good.”