This is an online exclusive story from ESPN The Magazine's Body Issue 2014. The Body Issue hits newsstands July 11. A complete list of athletes featured will be announced Wednesday on ESPN.com. Subscribe today!

The grass is a very big challenge for me. There are these low bounces and different movements, which is very difficult, especially for my height and weight. When the surfaces change and I start to play on grass, I start to feel it in the lower back and the lower hamstring. But I manage to move well. My first Grand Slam final was at Wimbledon, so I have no complaints about the grass.

It's not so bad that I can't touch my toes. But I'm not one of the most flexible guys. When you look at Novak Djokovic, you'd probably think he's made of rubber.

I have a mental coach. I think this is one of the parts of the game that not so many people talk about. I've worked with him for about five years now, and I think it's worked quite well. These days, tennis is about all the small details; if you can get 2-3 percent here and 2-3 percent there, it's just perfect.

I remember when Rafa [Nadal] was playing in shorts that were almost full-length pants. Now I'm the one who comes out and plays in the old-school short shorts. But I'm comfortable in them. I like to be in the position of doing something different.

That was the reason I got on social media. Tennis players need to be very focused and very intense, and I can show tennis players are not just hitting the little yellow ball and moving in between the white lines. I'm always trying to show my personality outside of the court.

My fitness guy sometimes makes fun of me. He says because of my legs and upper body, I'm two people in one. But being heavier down low, rather than up top, is what has been working in my case. The ideal plan would be skinnier and lighter legs and a little bit more on the upper body. But it's not something where you go into a store and say, "I want that."