Tennis fans may still be adjusting to the fact coaching during matches is now legal.
While it’s been happening discreetly throughout the history of the game, it only became legal last year for a player’s box to give instructions during play.
Stefanos Tsitsipas used to get in strife regularly for illegally being coached during his matches.
LIVE UPDATES: Australian Open day seven
READ MORE: Feud outed as former champ rips Australian Open villain
READ MORE: Djokovic sets a date with ‘quickest’ de Minaur
But on Sunday the law change worked against him, and into the hands of young Italian opponent Jannik Sinner.
Sinner was struggling and down two sets to the Australian Open No.3 seed, when he turned to his box and asked how he should deal with Tsitsipas’ second serve.
“He’s just been instructed by his coaching staff on second serves from Tsitsipas, to stand back,” Jim Courier noted on Nine.
“I’m pretty confident that the next time he sees a second serve, he’s going to be standing back there as well, and guys, I don’t know what you think, but I think it’s a good move for him.
“They just told him to go back. Coaching in play here.”
Watch the Australian Open live and free on the Nine Network: Channel 9, 9Gem and 9NOW.
Sure enough, on the next point Sinner stood further back to receive, and the tactic worked so well he broke Tsitsipas to take a lead in the third set.
He proceeded to win the set and take the match to a fourth, when a Tsitsipas victory had looked a fait accompli only half an hour earlier.
Sinner survives body shots
”A good decision by the coaching staff,” Tood Woodbridge said.
“They’ve got to be feeling really good.”
The decision to make in-game coaching legal divided the sport last year.
Tsitsipas was one vocal supporter of the move, having been penalised during his career for being coached from the stands.
“My coach has not been as discreet as other coaches, but it has been always happening. Trust me, it’s happening with almost every single player,” Tsitsipas said last year.
Tsitsipas clinches huge break in style
“The fact that it’s legalised now is going to make tennis a bit more peaceful, make players concentrate more on the game, less on different kind of nonsense.”
American player Taylor Fritz, on the other hand, was steadfastly on the other side of the argument.
“I really hate it,” Fritz said.
“It’s not something that should be a part of our sport.”
Whether players are for it or against it, there’s no doubt the rule change aided Sinner in the fourth round of the Open.
For a daily dose of the best of the breaking news and exclusive content from Wide World of Sports, subscribe to our newsletter by clicking here!