Novak Djokovic has been accused of breaking Australian Open rules

Novak Djokovic has been accused of breaking Australian Open rules in a viral video of another mystery drink

Serbian tennis champion Novak Djokovic’s brave run with an injured leg to the Australian Open final has been tempered by fresh allegations he may have broken tournament rules.

Footage has emerged of the Serbian star being given the mystery drink during his come-from-behind win over French player Enzo Couacaud in the second round of the Aussie Open.

It came during a match in which he gave up the second set and needed a medical timeout for his troublesome hamstring before progressing to victory.

His team sticks a label on the water bottle before handing it to a tournament official, who will hand it to Djokovic on the court.

The former world No. 1 carefully read what was on the label when he received the bottle.

The footage has raised concerns that Djokovic and his team may have broken rules governing when and where players can train during the Open.

Stars may only verbally communicate with their team when they are on the same side of the field. If they’re on opposite sides, signals must be used – which was the case when the footage was taken of Djokovic.

It is the third time in six months that the 21-time Grand Slam winner has caused controversy over his drink choice at a tennis tournament.

The incident came after Djokovic suffered a shock defeat to Danish teenager Holger Rune at the Paris Masters in November, after which a video of his physio fixing him a drink grabbed the headlines.

The physiotherapist was caught on camera mixing a mysterious drink in the stands before handing it to a ball girl to pass on to the Serbian champions. Another member of Djokovic’s team used his back to try and black out the view of what was going on.

A member of Djokovic's team hands the bottle with the freshly applied label to a tournament official, who will be handed it to him during the round two match at the Australian Open

A member of Djokovic’s team hands the bottle with the freshly applied label to a tournament official, who will be handed it to him during the round two match at the Australian Open

Djokovic took the time to read the label on the bottle carefully and some suggested it contained coaching notes from his team

Djokovic took the time to read the label on the bottle carefully and some suggested it contained coaching notes from his team

Previously, the 21-time Grand Slam champion attracted attention for apparently inhaling a substance from a water bottle at the Wimbledon Championships.

When asked what was in the drinking bottles, Djokovic only replied: “Magic potion”.

Many fans were quick to attack the star player for his repeated use of mystery drinks.

“There’s always a conspiracy when it comes to Djokovic,” one replied to the video.

“He does this all the time and seems to walk like the Roadrunner cartoon afterwards,” added another.

Other tennis fans thought the liquid itself wasn’t a problem, but the note attached to the bottle might be.

“Coaching notes maybe?” suggested one fan.

Others said it could be a sponsorship issue.

“A product made by a company that doesn’t sponsor it, so they cover up the label,” said one fan.

Others have been quick to defend Djokovic against anything undesirable, saying no one would be brazen enough to consume a banned substance in front of everyone.

“Too much attention for a teammate mixing sports drinks,” wrote one fan.

“A really ridiculous notion that there’s something going on, the stadium full, cameras everywhere, drinks mixed up in the players’ box… I mean, use a little logic here, maybe they don’t want to give anyone the advantage.

Fan holds up a banner in support of Serbia's Novak Djokovic during his third round match against Bulgaria's Grigor Dimitrov

Fan holds up a banner in support of Serbia’s Novak Djokovic during his third round match against Bulgaria’s Grigor Dimitrov

Djokovic has a history of keeping secret his bottles of 'magic potion' and has been questioned three times in the space of six months about the use of mysterious liquids

Djokovic has a history of keeping secret his bottles of ‘magic potion’ and has been questioned three times in the space of six months about the use of mysterious liquids

“In addition, in a locker room, you see a team of players who always prepare drinks in unmarked bottles and put them in the fridge. Training programs, taking dietary supplements, etc. are trade secrets.’

Another tennis fan pointed out that Djokovic had already been acquitted at Wimbledon for drinking a “mysterious” drink that turned out to be isotonic.

“I hope you all had Wimbledon’s statement under your eyes so you can relax. It’s isotonic, very popular with athletes,” they wrote.

“It comes in powder form and can be mixed with water or taken dry and then taken with water.

Australia's Alex de Minaur is the last native left in singles and has a big task ahead of him in Djokovic

Australia’s Alex de Minaur is the last native left in singles and has a big task ahead of him in Djokovic

“Hard to believe people are stupid enough to think an athlete would take a banned substance where thousands of spectators and cameras can see you. They are regularly tested before and after games and also outside of the game.”

Another fan wrote, “Every athlete has sports, vitamin fortified and electrolytic drinks with the purpose of helping athletes replenish glucose, fluids and electrolytes lost during strenuous activity.”