Nick Kyrgios never seems too far from controversy, but his latest actions, namely a propensity for the underarm serve, appears to have split opinion in the tennis world.
Kyrgios provoked Rafael Nadal to say the Australian "lacked a little bit of respect" after he produced an underarm serve during their match at the Mexican Open in February.
More recently, the world No 33 pulled out the tactic twice against Serbia's Dusan Lajovic during their Miami Open third round encounter, sparking fresh debate over the tactic. Kyrgios won the match 6-3, 6-1 in less than an hour.
Kyrgios is no stranger to scandal and has been sanctioned for a litany of tennis offences. In three successive years at the Shanghai Masters, he exited in controversial fashion: last year and in 2016 he was accused of tanking, while in 2017 he stormed off the court midway through his first round match against Steve Johnson.
Then there was the unsavoury incident in 2015 when Kyrgios made unsavoury remarks to Stan Wawrinka about his girlfriend, fellow tennis professional Donna Vekic.
But despite his many brushes with the tennis law, Kyrgios' underarm serving is perfectly within the rules of the game, even if the tactic is frowned upon.
Kyrgios defended his underarm serving during an interview with the Tennis Channel when asked about the incident against Nadal.
"I think it's a tactic, for sure. Especially with Rafa - I was starting to feel my legs cramp up so I needed a free point at any cost," Kyrgios said. "He's standing so far behind the baseline, so I thought the underarm serve might break his rhythm."
The attempt against Nadal ultimately didn't pay off, with the serve floating out, but it looks as though Kyrgios has spent some time perfecting the shot.
The first attempt at 3-1 in the first set against unseeded Lajovic might have been regarded as text-book execution, if there existed such a consensus. With the Serb standing well behind the baseline, Kyrgios leaned over the ball, bounced it a few times and without looking up, flicked it just over the net.
It landed with enough slice to bounce twice for an ace and seal the game, leaving a flat-footed Lajovic no chance to reply.
More casually struck, Kyrgios's second effort lacked something in execution, allowing Lajovic to swoop in and easily make the retrieve. But the Australian was ready for the Serb's drop-shot return, and flicked it past him to close out the first set.
Certainly effective, but the underarm serve has created a debate over whether it blurs the lines of sportsmanship.
Judy Murray, the British tennis coach and mother of grand slam-winning brothers Andy and Jamie, is of the strong belief that the shot should be applauded.
"The whole point of tennis competition is to disrupt your opponents game by applying pressure through changing the speed, spin, direction, depth or height of the ball," she wrote on Twitter. "And that includes the serve. Kyrgios is a genius. I’m surprised more players don’t do it.
"Not many people understand genius or know what to do with it so they try to get genius to conform to something they do understand. Kyrgios has uncanny instinct and vision. He’s unpredictable and has phenomenal creativity and hand skills. Yes he’s mentally inconsistent but he’s a genius.
Kirsten Flipkens, the Belgian former world No 13, agreed with Murray, commenting on the Scot's social media post by writing: "Alright. Approved by Judy. Let's do this."
Roger Federer, arguably the greatest male tennis player of all time, said he has no problem with the underarm serve, saying: “Yeah, underarm is definitely a tactic, I believe, especially when guys are hugging the fence in the back.
"From that standpoint,you shouldn’t be ashamed if you try it out, you just look silly if you miss it sometimes. Why not try it?
"The problem is like in practice, you never really try it. When you come out in the big stage in front of a full crowd, tricky to pull off.”
Kyrgios is certainly not the first player to deploy the underarm serve. Five-time grand slam champion Martina Hingis famously pulled one out during the 1999 French Open final against Steffi Graf, leading to loud jeers from the Roland Garros crowd.
And Kyrgios certainly won't be the last player. However, such is the wider fascination with the Australian and his burgeoning reputation as a divisive figure, each time he tries the underarm serve it is sure to attract attention and debate.
Yet, while the tactic is within the laws of the game he, or indeed anyone else, are well within their rights to try it. After all, who determined how a certain tennis shot should be played?