Rafa Nadal is already a great and may in a few years be classed the best to ever wield a tennis racquet - but the Spaniard has shown a continuing disregard for tennis etiquette which may eventually prompt a change in the rules of the sport.
Last Sunday's Australian Open final against Stanislas Wawrinka, where Nadal was hampered by a back injury, was an unfortunate climax to a brilliant tournament.
There is no disputing that the 27-year-old was injured but the timing of his call for medical attention was again controversial.
In tennis, you're supposed to call for a medical time-out ahead of your own serve, rather than before your opponent's attempt to hold serve - especially in bigger matches where the wait and subsequent cool-down of muscles and mind can dramatically disrupt the rhythm.
It's an unwritten rule but usually adhered to, especially at the top level. But Nadal called for the trainer immediately after being broken in the second set against Wawrinka.
He was clearly injured but it often happens when he's struggling on the scoreboard; in the vast majority of his grand slam losses, dating back to the 2007 Wimbledon final against Roger Federer, Nadal has taken a medical time-out directly before his opponents' serve. On other occasions, a medical time-out has seemed to change the course of a match in Nadal's favour.
In 2010 at Wimbledon, Nadal was in serious trouble against Philipp Petzschner in the third round, trailing two sets to one and down a break in the fourth set when he called for the trainer for treatment on his knee. After the break, Nadal broke the German's serve (Petzschner seemed to be clearly rattled) and stopped his momentum, eventually winning the match in five sets.
"I don't know, maybe he had something [an injury]," said Petzschner after the match. "Maybe it was just a clever part to take a time-out there. I don't know."
There were also famous occurrences against Federer in finals in 2008. In Monte Carlo, the Swiss was leading in the first set when Nadal sent for medical attention. When the treatment was finished, Nadal stormed back to win the set and the match. In Hamburg the same season, Nadal called play to a halt (due to a thigh injury) just before Federer was to serve for the set. When the game restarted, Federer was broken and he eventually lost the match.
The issue really came to the fore at last year's Australian Open, after Victoria Azarenka's semifinal victory over Sloane Stephens. Azarenka served for the match at 5-3 but blew five match points with a series of nervous shots and was eventually broken. Just before Stephens was about to serve to stay in the match, Azarenka called for the doctor and spent 10 minutes off the court. She seemed to regroup mentally, while Stephens sat waiting courtside, and then broke the American to progress to the final.
Asked about the time-out after the match, she admitted to almost doing "the choke of the year" and feeling a little bit "overwhelmed" as "nerves got into her". She later said, as vitriol flowed about this perceived gamesmanship, that she was having trouble breathing and felt constricted in her chest.
Currently Nadal and Azarenka are doing nothing wrong, according to the rules of tennis, and it is part of gamesmanship to do everything possible to unsettle an opponent. It is also difficult to criticise Nadal too much. He does have a fragile body and plays an extraordinary number of matches, so injuries and niggles are inevitable. He is probably the toughest mentally on the circuit and handles physical and mental adversity better than anyone.
But something needs to change. One commentator has suggested rules to ensure players can take injury time-outs only before their own service games. If they want a time-out before an opponent is about to serve, they should immediately forfeit that game. It's worth considering.