Black Tennis Pros

In addition to stripping down for the issue, Williams exposes harrowing new details about her ongoing battle with Sjogren's syndrome, an autoimmune disorder that, according to the Sjogren's Syndrome Foundation, causes white blood cells to attack a person's moisture-producing glands.

"At my worst point, I wasn't able to play tennis at all," says Williams. "Just the whole quality of my life was compromised. You are so tired it hurts. You have to accept that you're never going to be 100 percent."

Williams, who was forced to stop playing for more than six months in 2011-12 because of the illness, reveals how she was able to work her way back up the rankings.

"Because of Sjogren's syndrome, I have to be careful," she says. "If I train too hard, then I won't be able to do anything the next day. There would be times when I'd park my car at home and I fell asleep behind the wheel because I was so tired. It's a balance between pushing myself as much as I can and being reasonable about what I can achieve and what my body will tolerate."