Jonas Bjorkman has a simple explanation for the remarkable defeats suffered here at the Australian Open by Andy Murray and Novak Djokovic, the world’s top two players.

“They’re human,” said the Swede, who coached Murray until the start of last year. “Out of 100 matches they play high quality in 99 of them and then in that one match out of 100 we are all surprised when they don’t.”

Murray was flying back to Britain on Monday after his stunning fourth-round loss to Mischa Zverev, the world No 50, whose serve-and-volley tactics and repeated net approaches appeared to throw the world No 1 out of his stride.

The 29-year-old German, who until last week had never gone beyond the second round here, was the lowest ranked player to beat Murray at a Grand Slam event for 11 years. Three days earlier Djokovic had lost to Denis Istomin, the world No 117.

“Normally you would see Andy or Novak get out of situations like that, but this time they had guys against them who managed to control their nerves and that made all the difference,” Bjorkman said.

“The two of them have been exceptional. They always have such high standards in the big tournaments and it’s a shock when they go out early. We’re so used to them being quarters, semis minimum.

“But Istomin did not make mistakes against Novak, who didn’t hit the ball as well as he usually does. As for Andy, I was surprised to see him not striking the ball as well as he usually does. Normally he likes the target coming in so he can hit the passing shots, but against Zverev he just couldn’t find the rhythm.

“He’d played Mischa before, so he knew exactly what to expect, but you get confused when you’re not ball-striking as well as normal. You try to hit it to the corner and it goes all of a sudden half a metre away from that.

Murray was outplayed by his German opponent in Melbourne (EPA)

“I think he got confused. He has the best lob in the game, but by his standards he hit so many short ones, which is very rare and unusual.”

The former French Open champion, Michael Chang, who coaches Kei Nishikori, agreed. “Mischa is obviously a unique player,” he said. “He doesn’t give you a whole lot of rhythm. It was probably one of the few times when Andy looked like he had lost his timing.

“Zverev was playing very craftily, picking the right times to attack and go for his shots. You don’t normally see Andy struggle against players who come in because his lobs and his passes are so good, but Zverev was able to find a way to get him off his game, so that Andy wasn’t hitting the shots that he normally hits.”

Pat Cash, who won Wimbledon in 1987 playing serve-and-volley tennis, believes that the German won a mental battle. “What serve-volleyers typically do is to get into your head,” he said. “And once you can get into a player’s head it makes it really tough. Even the simplest passing shot is really tough. We saw that yesterday.”

He added: “To see a guy serve-volley on second serve and beat the world No 1, who is allegedly one of the best returners and best passers of all time, and just get knotted up and not even able to hit a passing shot, it was really impressive to watch.”

Mischa Zverev celebrates after beating Murray (Getty)

Cash thinks Murray could have been more positive. “He was a bit passive, a bit negative, but the conditions were really quick,” the Australian said. “That sliced backhand that Zverev played, just pushing the ball around, was really tricky to attack, but time and time again Andy had the opportunity to come in and finish the point off [but chose instead] to see a floating forehand or backhand drop near the baseline.”

Another former Wimbledon winner saw Murray’s defeat as a “missed opportunity”. Goran Ivanisevic, the 2001 All England Club champion, said: “I never thought he could lose to Zverev because his defending is the best, but Zverev came to the net and gave him no rhythm. Andy was not 100 per cent and didn’t play his best tennis.”

Chang thinks Murray’s defeat will be “just a hiccup”. He added: “Unfortunate losses happen. I don’t think he’s going to get too down on it. He’ll just try to learn from it and move on.”

In theory Murray will next play in Britain’s Davis Cup tie away to Canada beginning in 11 days’ time, but he may decide that he needs to rest instead. The Scot had a short off season and faces a busy time from the end of next month, when he is due to play in Dubai, Indian Wells and Miami. Leon Smith, Britain’s captain, will announce his squad for Ottawa on Tuesday.

Dan Evans' best-ever run at a Grand Slam came to an end against Jo-Wilfried Tsonga (Getty)

Dan Evans, who described the chances of Murray playing in the tie as “a pretty large if”, also flew home on Monday but has already committed to travelling to Canada next weekend. If Murray is missing from the team, Evans and Kyle Edmund are set to be Britain’s singles players, with Jamie Murray and Dominic Inglot playing together in the doubles.

Evans, who played in Perth in the first week of the new season and reached his first tour final in Sydney in the second, has some serious globe-trotting ahead of him. After Ottawa the 26-year-old from Birmingham is due to play in Dubai before flying back to North America for the Masters Series tournaments in Indian Wells and Miami.