Seven-time Grand Slam champion John McEnroe has claimed that Andy Murray is still some way short of achieving the level of dominance the likes of Novak Djokovic, Rafael Nadal and Roger Federer have enjoyed in recent years.
Murray will go into the upcoming US Open as the form player in world tennis having triumphed at Wimbledon before claiming Olympic gold in Rio de Janeiro earlier this month, while Djokovic suffered early elimination from both tournaments.
McEnroe acknowledged that the world number two is in the form of his life, but still sees Djokovic as the man to beat at Flushing Meadows.
"Can Murray dominate now? I think Novak is still obviously the most obvious obstacle. He's been playing at a level the last couple years that Murray hasn't been able to attain. That's frustrated him. Things have changed the last couple months, the shock that he lost early at Wimbledon, but to me the level that Novak was playing, it was higher consistently. The bar was higher maybe than anything I've ever seen as far as his consistency," he told ESPN.
"There's a way to go where he would be able to lift it to do what Novak has done the last couple of years and is going to continue to try to do. And Nadal on clay, at a French Open, you're not going to convince me he's done yet the way he was playing leading up [before withdrawing injured] - I thought he was getting close to what he was before on the clay. That would be an interesting match, to say the least, with Murray. I don't think Murray would go in as a favourite on that surface against Nadal in a best-of-five.
"Murray is playing the best tennis of his life. He seems to have everything in order. He's in a good space. He wants to get closer to be talked about in the same breath as these three guys that are like three of the five greatest players that ever lived. So Murray has been meticulous. He's done a great job. But he's still got a ways to go to even get close to those guys."
Murray won the US Open in 2012 and goes into this year's edition having reached the final of the last seven tournaments he has played in.
