Nick Kyrgios needs to grow up quickly

When does a loveable rogue become a dislikeable brat? Nick Kyrgios could be about to find out. Until now many people in tennis have been prepared to give the 20-year-old Australian the benefit of the doubt despite his many misdemeanours – on the basis that he brings some much-needed youthful vitality to the sport – but this latest incident may change opinions. Clashing with authority, whether in the shape of match officials or administrators, is one thing, but offending a fellow player – and a highly popular one at that in Stan Wawrinka – is on another level.