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.