As Novak Djokovic was concentrating on his rehabilitation from a knee injury with the diligence of a specialist preparing for surgery, the Serbian was quizzed by his wife Jelena, who asked him a simple question. Why? Why was he pushing so hard to return to Wimbledon, where he is a seven-time champion, less than three weeks after undergoing surgery on a torn meniscus which forced him to forfeit a quarterfinal at the French Open?