Bizarre footage has emerged of Novak Djokovic’s team apparently attempting to conceal something being poured into the Serbian star’s water bottle mid-match.

The video, taken during Djokovic’s third-set tiebreak win over Stefanos Tsitsipas in the semifinal at the Paris Masters on Sunday, appears to show his entourage mixing up a concoction while courtside.

The yellow drink bottle was then handed to a ball kid, who took it to Djokovic.

The fan video also appears to catch the moment Djokovic’s team realise they are being watched. One member of the group can be seen moving to shield the bottle from view.

The footage, originally shared on Twitter, has gone viral after it was shared by journalist Damian Reilly.

“Can anyone who knows tennis explain what is going on here, and why it’s being done this way? It looks amazingly dodgy,” Reilly wrote.

“The lack of curiosity about this from the tennis media is astonishing. He literally told a room full of journalists he was taking ‘a magic potion’ during Wimbledon, and they just fell about laughing.”

Tweet from @DamianReilly

At Wimbledon, Djokovic repeatedly refused to reveal what he drank from a bottle while on-court. He brushed it off as a “magic potion” before claiming he couldn’t reveal what was inside just yet.

“It’s a magic potion, that’s all I can say,” he said.

“You’ll find out soon but I can’t speak about it now.”

There is no suggestion the Serbian former world No.1 has done anything wrong. But the footage has sparked further calls for more transparency around substances taken by players, including from leading tennis journalist Ben Rothenberg.

“I’ve always thought there should be more transparency about the substances players take, particularly during matches, but I’ve also rarely thought anything was likely amiss,” he said in a tweet.

“But golly, the body language in this video is bizarre. What does the Djokovic team think needs hiding?”

“I think rivals [and the public and the officials governing the sport] should get to know [the substance]. I don’t think there should be secret substances being ingested during competition.

“I’m accusing no one of anything here, but what an incredibly suspicious way to start acting when you suddenly notice that you’re being filmed. [I] Hope Djokovic and/or his team get asked about this today in Paris, and that they don’t just accept his previous ‘magic potions’ answer.”

Djokovic was stunned by Danish teenager Holger Rune in the final of the Paris Masters. The 19-year-old defeated Djokovic 3-6 6-3 7-5 in Sunday’s final, fending off the six-time champion at the indoor hardcourt event to earn a place in the top 10 for the first time and becoming the first Danish man to reach such giddy heights.

Addressing Rune in an on-court interview, Djokovic said: “You absolutely deserve this victory. What an amazing week you had.

“I’m not happy that you beat me, but on the other hand I’m happy for you because I like your personality, I think you’re a very dedicated guy that loves tennis and puts a lot of hours into hard work.

“It’s paying off for you, and I’m sure the future is bright for you and your team, so congratulations.”

Djokovic was not asked about the issue with the drink bottle following his finals loss.

-with AAP