Hitting an inviting short ball at an opponent who has moved towards the net is another common flashpoint.

Tsitsipas, regularly at the centre of drama, decided tagging Altmaier was fair game following his opponent’s underarm serve.

“Next time, don’t wonder why I hit you, OK? I’m just saying, if you serve underarm…” Tsitsipas told Altmaier at the net.

It is not the first time Tsitsipas has drawn ire for trying this tactic.

Targeting Arthur Fils’ body in Rome earlier this year did not pay off, as the incident fuelled the Frenchman on his way to victory.

Doubles player Andrea Vavassori was less pleased in Monte Carlo when he was struck in the ribs by American opponent Ben Shelton – who then labelled the Italian “soft”.

Norrie thinks hitting a ball at an opponent is fair game.

“Obviously you apologise but I think that’s a perfectly good play – it’s usually the best option to go middle,” he said.

“It’s good to acknowledge what you’ve done but you move on, man.

“If you’re hit with a tennis ball it’s not the end of the world – it’s not like we’re playing rugby.”