Now 31, and figuring out from day to day how to handle an illness that saps her strength, Williams was on the wrong end of a lopsided 60-minute defeat in the second round of the French Open on Wednesday.
Looking glum and lacking the verve that carried her to seven Grand Slam titles, Williams barely put up any resistance and lost 6-2, 6-3 to No. 3-seeded Agnieszka Radwanska of Poland at Roland Garros. Coming a day after her younger sister Serena was stunned in the first round by 111th-ranked Virginie Razzano of France, the early exit marked the first time in 43 major tournaments with both in the field that neither Williams got to the third round.
''I felt like I played,'' Williams said after making a hard-to-fathom 33 unforced errors, 27 more than Radwanska. ''That pretty much sums it up.''
This one was not exactly an out-of-nowhere upset, considering that Williams is ranked 53rd now, never has been as good on clay as on other surfaces, lost to Radwanska 6-4, 6-1 two months ago, and is learning how to be a professional athlete with Sjogren's syndrome, an autoimmune disease that can cause fatigue and joint pain.
Still, the meek way Williams departed was striking, considering that she has been ranked No. 1, has appeared in 14 major finals to Radwanska's zero, and from 2008-10 won 10 of the 11 sets the two played against each other.
''I don't know if I ever asked myself, 'Why me?' I mean, obviously it's frustrating at times. I don't know if there's anything mental more I can do at this point, but there's a lot of stages to go through with this kind of thing,'' said Williams, whose fastest-in-the-game serve was broken five times Wednesday. ''There's a lot of people who have it a lot worse than I do. I'm still playing a professional sport, so I have to be very positive. And I'm going to have ups and downs. I haven't gotten to the 'Why me?' yet. I hope I never get to the 'Why me?' I'm not allowed to feel sorry for myself.''
It's hard to know, however, how much energy she'll have from one day to the next.
Whenever the alarm goes off, Williams starts to find out what the next 24 hours will be like.
''Every morning is different. Some mornings, I don't feel great, then it's a better day than I thought it was going to be. I can't automatically be discouraged. When I wake up, I just have to see how it goes. Sometimes I get a second wind,'' she explained. ''It's just so hard to know.''
Williams revealed her diagnosis in late August at the U.S. Open, when she withdrew before her second-round match. She skipped the Australian Open in January, before returning to the tour in March in a bid to earn a berth on the U.S Olympic team. Spots are awarded based on rankings - the top 56 get in automatically, with a maximum of four per country, so Williams should be OK.