In an interview to ESPN, John McEnroe commented on Roger Federer's ability to improve and evolve. The American said: "Personally, I think Roger has got less stubborn, switching to the bigger frame racket. Obviously he won so much with a 90-inch frame, but he had problems, especially with Nadal.
That lefty serve, catching the ball with that spin, above his shoulders -- that's a tough shot for a one-hander to handle. I think that was a realization, that if he didn't make some changes he wouldn't be able to keep improving, and if these other guys kept improving he wouldn't be able to stay with them.
So I give him credit." John continued: "These guys just got it so quickly. I can tell you from personal experience that I felt like I waited on a little bit, to sort of see what my opponents would do instead of going, "Look, just keep adding no matter what because they're going to try to add something."
That's one thing I admire about all three of these guys, because they keep saying, "OK, what can I do to get better?"