Roger Federer is 36 years old and still dominates the world rankings in tennis, but he’s an anomaly in the tennis world. Novak Djokovic, Andy Murray, Rafael Nadal and Garbiñe Muguruza who all used to occupy the top spots in the sport are facing a series of troubling injuries and mid-match retirements. Is the long tennis season to blame as the injuries continue to mount? Or could it be technology’s fault?