A most unusual upset for Serena

— -- LONDON -- Walking off court on a fittingly dank and gloomy English day, Serena Williams said confusion dominated feelings she could neither identify nor express even an hour later.

"Right now, I don't really know what I did wrong," Williams said after being ousted by No. 25 seed Alize Cornet 1-6, 6-3, 6-4 in Wimbledon's third round Saturday. "Usually, I do. Usually, I know I did this, this and that."

"Usually" -- and maybe this is the most confusing part for those who have watched Williams over the past 17 years -- is a word we perhaps can no longer ascribe to the most dominant women's tennis player of her generation.

Usually, Williams, a five-time champion here, wins at Wimbledon. But this was the second year in a row in which she failed to make the quarterfinals. (It ties her earliest loss ever at Wimbledon, with 1998 and 2005.)

Usually, Williams rises to dominance in Grand Slam tournaments. But with Saturday's loss, it marks the worst three-Slam sequence of her career after fourth-round, second-round and third-round exits in the Australian Open, French Open and now Wimbledon. It is also the first time she has lost in the first week of back-to-back Grand Slams since 1999.

And usually, Williams turns opponents into jelly. But Cornet was masterful, aggressive, unafraid, a phenomenon Williams claimed in several matter-of-fact but annoyed declarations is not so usual at all.

"I think everyone in general plays the match of their lives against me ..." she said. "So I just have to always, every time I step on the court, be a hundred times better. If I'm not, then I'm in trouble. ...

"If I'm not playing, you know, a great, great match, these girls, when they play me, they play as if they're on the ATP Tour, and then they play other girls completely different. It's never easy, you know, being in my shoes. But you got to be ready."

But Williams said she was ready after her French Open shocker this spring, a tournament in which she played "really bad," she said, in a 6-2, 6-2 loss to Garbine Muguruza, the most one-sided Grand Slam defeat of her career.

"Here I actually thought I played better," Williams said. "I came into the tournament in better form. I worked really, really hard coming into this event."

More confounding was that after emerging from a rain delay tied 1-all and at deuce, Williams reeled off the next five games to take the first set of a match that appeared to be heading the way of her first two matches, in which she dropped a combined five games.

But at that point, Cornet, who defeated Williams in straight sets on the hard courts of Dubai in February, took the aggressive route while Williams retreated -- often uncharacteristically rooted behind the baseline, which made her particularly vulnerable to Cornet's deft drop shots. Williams' usually reliable serve also deserted her when she needed it most.

And Cornet said she also thought Williams "lost concentration" early in the second set.

"I used it to come back in the match, and finally I played way better from the beginning of the second set," Cornet said. "I think then the battle was on."

Cornet, 24, who equals her best Grand Slam result with Saturday's victory, seemed more shocked than anyone, kissing the court after match point.

"A few years ago, I couldn't play on grass. I was so bad," Cornet told the BBC, then informed the assembled media it was her first visit to Wimbledon's main interview room.

"I'm just calming down now because I was very excited for an hour," she said. "I couldn't believe it. I still cannot believe it, actually. If somebody would have told me a couple years ago that I would be in second week here in Wimbledon, beating Serena, I wouldn't have believed it."

Williams' loss once again opens up her quarter of the draw where, as in the French Open, resides Maria Sharapova, an easy 6-3, 6-0 winner Saturday over American Alison Riske. The best guess from most experts was that Sharapova and Williams were destined to meet in the Wimbledon quarterfinals.

For Williams, seemingly consoling herself even in obvious despair, she spoke of studying video and getting better.

"It's OK ... sometimes it happens," Williams said. "You know, you work hard, maybe it's not for today, maybe it's for tomorrow. I just got to keep going."

For the immediate future, she continues in Wimbledon doubles with her sister Venus, also eliminated in the third round of singles. It is the first time in eight years neither Serena nor Venus will be competing in the second week here in singles.

"I told Venus the other day like, I don't even want to play because I'm so bad right now," Serena Williams said. "She should get a new partner."

Ostensibly, she was kidding. But Williams will turn 33 in September and the retirement questions have already begun leaking into the conversation. But just as surely, she fended them off.

"You know, just 'cause you lose a match doesn't mean you stop," she said. "You just got to kind of keep going. Like I said, maybe it wasn't for today. Maybe it's for tomorrow. So I'll just keep fighting. That's all I can do really.

"I know that I can do better. I know that I have potential to continue to be on top. So hopefully that's what keeps me motivated."