By Jon Wertheim Jon Wertheim answers this in his latest mailbag, plus the value of coaches in the sport and whether there are inconsistencies in how players are disciplined for on-court antics. PARIS — As it is written, Wednesday is Mailbag Day. If you didn’t catch it, here are some bleary-eyed thoughts on the latest Rafael Nadal–Novak Djokovic clash from Tuesday. And now, onward … What’s next for Djokovic?Jon, It will have been a year now since Djokovic has won a major. He has changed coaches. He has the whole COVID mess, which has clearly affected him. His confidence doesn’t seem fully back….