Murray isn't going to put a dent in Djoker for the forseeable future. Federer at his best can give Novak a run out... but I think we're in three set territory these days. Nadal is the big question mark... we'll have to wait until the 2016 Clay season.... Other than that it takes an outlier like Wawrinka playing out of his skin and redlining for 3 or 4 hours. It's also kind of concerning that we seem to have a lost generation of mediocrity just behind. Younger guys like Kyrgios et al are going to have to step up over the next couple of years to fill the vacuum.