Elite players led by world number one Roger Federer expressed their concern at the Cincinnati Masters that Rafael Nadal will be forced to miss the US Open due to left knee tendinitis. \"It\'s not a surprise, because I wrote him and he told me it wasn\'t looking good at all,\" said top seeded world number one Federer. \"I kind of saw it coming. But obviously when it\'s official it\'s disappointing for tennis, there\'s no doubt about it. \"I would love to have him in the draw. With 12 days before the Open you figure he might still have time to fix what he has to fix to get ready. \"If he pulls out that early before the Open, it must be something serious. That\'s what is sort of scary. There is obviously the whole debate going on if he is going come back for this year. \"I hope in hindsight this is a very smart decision by him. But it\'s obviously a big blow and disappointing news for the tennis world.\" Those sentiments were echoed by number two Novak Djokovic and fourth-ranked Olympic gold medallist Andy Murray. \"He\'s a great competitor, somebody I know really well on and off the court,\" Djokovic said. \"I\'m sure that if he was able to perform in US Open he would come. So I wish him a quick recovery.\" Murray, who had been dealing with a knee problem of his own over the last week or so, was equally sympathetic. \"I\'m disappointed for him, it\'s obviously tough. He\'s had trouble with his knees in the past. So I hope he can rest, doesn\'t come back too early, and gets them fixed so he can get back to playing his best tennis.\"