Just as when she was beaten by obscure fellow American Craybas at the same stage in 2005, no one saw it coming.
Especially when, after a frustrating four-hour rain interruption, the 32-year-old five-times champion returned to Court Two in the early evening to romp through an opening set that lasted only 29 minutes.
Victory for top seed and most people’s pre-tournament favourite looked a formality, but Cornet, the world number 24, had other ideas and began a stirring fight back to claim a 1-6 6-3 6-4 victory – her second over Williams this year.
Williams seemed as mystified as everybody after the defeat, which came a round before last year’s exit to Sabine Lisicki and a day after sister Venus went out against former champion Petra Kvitova, meaning neither sister has reached the second week of the singles for the first time in eight years.
“Right now I don’t really know what I did wrong,” Williams told reporters. “Usually I do. Usually I know I did this and that. I have a few ideas, but this will be a really good one for me to kind of like assess and figure out.”
Whereas Williams had been in total command against an apparently overwhelmed Cornet, the match suddenly flipped during the early stages of the second set when the Frenchwoman cut loose.
“I think the rain delay killed me a little bit because I started the match very well, like the two first games were really good,” Cornet said.
“After that, I think she lost a little bit (of) her concentration in the beginning of the second set and I used it to come back in the match, and finally I played way better.”
Still, the crowd expected Williams to flick the switch and recover but as the errors mounted and she began to look more and more awkward and hesitant, the match began slipping away.
With desperation in her eyes Williams roared in Cornet’s direction after saving a break point in the opening game of the third set but she dropped serve at 2-2 in the decider and quickly went 5-2 down before mounting a fightback.
When Cornet, who had never beaten a top-20 player in a grand slam, served for the match at 5-4 it seemed inevitable that her nerve would fail her. But just like the 30-year-old Craybas nearly a decade ago, she seized her chances.
Instead, it was Williams who cracked, bungling a dreadful volley into the net to give Cornet a match point and then missing a passing shot to bow out.
Rather than scold herself, however, Williams said Cornet had raised her game.
“I think everyone in general plays the match of their lives against me,” she said. “So I’m pretty sure that the next match, it won’t be the same.
“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.”
It was Williams’ earliest exit at Wimbledon since that defeat to Craybas and means she has failed to reach the quarter-finals of the year’s first three grand slams.
She remains one behind the 18 grand slam titles won by Chris Evert and Martina Navratilova and four behind Steffi Graf’s professional era record of 22, but while the flow of silverware has slowed this year, Williams remains hungry for more.
“I think it’s definitely pretty significant,” she said of at least emulating fellow Americans Evert and Navratilova.
“It’s something I’m obviously going to keep going for. It’s definitely something in my mind, pretty important.”
(Editing by Pritha Sarkar/Greg Stutchbury)