'Machine' Djokovic sparks injury debate after Melbourne masterclass

Novak Djokovic's seemingly remarkable recovery at the Australian Open prompted debate on Tuesday and raised the question: when is an injury not an injury?

The 35-year-old Serb was battling a left hamstring problem before the Grand Slam began last week as he chases a record-equalling 22nd major crown.

The red-hot favourite has required medical treatment during matches, worn heavy strapping and said a few days ago that he was not able to practise.

It appeared the injury could even torpedo his tournament altogether.

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And yet there he was on Monday, the strapping still there but the former world number one moving freely to sweep past home hope Alex de Minaur 6-2, 6-1, 6-2 and into the last eight.

It was an ominous warning of intent from Djokovic and he said afterwards that the hamstring was so improved that "I didn't feel any pain".

He thanked his medical team and said he had been popping anti-inflammatories, something he does not like to do.

"It's been honestly exhausting to be involved in a lot of different treatments and machines and stuff that we do," he said.

At his post-match press conference, De Minaur - who noted how well Djokovic was able to move around the court - was asked about his opponent's hamstring and all the fuss around it.

"It's the only thing everyone's been talking about," said the 23-year-old.

"Today I was out there on court against him. Either I'm not a good enough tennis player to expose that or... it looked good to me."

The Australian subsequently took to Twitter on Tuesday to hit out at headlines which took his comments as casting doubt on how injured Djokovic really was.

Speaking to Serbian media at Melbourne Park, Djokovic