I have a very strong opinion. I'm absolutely against it. I'm against the challenge system. I'm for the way it is right now. Don't change that.

When you're good at something, make that everything

I'm at the top of my game so, when I win or lose, I don't freak out...I don't think we can call it a rivalry yet. There's just to many great players around.

Having twin girls is a life changer - that's for sure. But I like getting up and changing diapers. It's the things you do.

I'm as patient a father as I am on the tennis court. It takes a lot for me to get really upset, but sometimes kids can get you really cross if they really keep bugging you.

The week before the (US Open) I gave a few interviews for CNN, USA Network, New York Times, USA Today and Sports Illustrated which had been arranged beforehand. The reason for giving these interviews is not only because working with the media is just part of the job, it is much more my desire to contribute to the promotion of tennis in the U.S.

It is always in my mind still that I can crush anybody. That's not an issue. But I think that is the same for most athletes. If you don't believe you can win tournaments anymore, then you can't do it.