Tennis stars bizarrely swap ends mid-game after never-before-seen error, even the umpire was confused

Young tennis stars Arthur Fils and Luca Nardi were forced to change ends in the middle of a game during their round-robin match at the Next Gen ATP Finals.

Spectators were left confused when the umpire stopped play at 40-0 and proceeded to have a lengthy chat with the two players before the pair were told to swap sides.

Fils, who is the favourite for the tournament, was preparing to serve when umpire Mohamed Lahyani stepped in, prompting confusion both on and off the court.

Despite Lahyani's experience, it was a new rule that caught the umpire out and he was forced to correct his mistake.

"It's 40-0, you go there and serve. It's how it is", Lahyani told Fils.

"It's 4-2 you have to be there."

"I lost this game, it was 3-2, 4-2," Fils, who is seeded at world No.36, said.

Lahyani replied: "You have to be on this side."

Flis' opponent Nardi jumped in: "But why? Because it's the rule?"

Lahyani continued: 'Yes that is the rule.'

"Every set? Doesn't matter what is the score?" A confused Nardi responded.

Lahyani then finalised his decision: "You should be there, yes. So now you go, 40-0 you go there."

The process took almost a minute before play was allowed to continue, with Fils resuming the game by serving from the opposite end to which he started the game.

The Frenchman didn't allow the antics to get the better of him as he came from behind to defeat Nardi three sets to two.

Safe to say this might not be a rule they consider at the top level.