The other Williams sister, Venus, is roughly a year past receiving a diagnosis for Sjogren's syndrome, an incurable autoimmune disease that can cause fatigue, joint pain and dryness of the eyes and mouth.
Feeling "beat up," she withdrew from the 2011 U.S. Open after one match and has played only eight tournaments since. Now 32 and four years past her last major tournament victory -- her seventh overall -- the two-time Open champ has entered this week's tournament "doing a lot better than this time last year. So much better."
She skipped the first of the four Grand Slam events, the Australian Open, in January, was eliminated in the second round of the French Open (by No. 2 Agnieszka Radwanska of Poland) and the first round of Wimbledon (by No. 79 Elena Vesnina of Russia).
But she teamed with sister Serena to win both the Wimbledon and Olympics doubles titles and advanced to last week's semifinals in the suburban Cincinnati hard-court tournament.
She has learned, she said, that "if I wake up and don't feel great, just kind of hang in there, not panic. I'm eager to get matches. I know I can play great tennis. Nothing can prevent bad days, but the bad days aren't as bad as they used to be. I'm learning to deal with it."