Betrayed by her backhand and, more surprisingly, her usually dangerous serve, five-time Wimbledon champion Williams lost to 25th-seeded Alize Cornet of France 1-6, 6-3, 6-4 Saturday in the third round at the All England Club.
''If I'm not playing 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,'' Williams said, rolling her eyes. ''It's never easy being in my shoes.''
It's her earliest exit at the All England Club since 2005, when she also was beaten in the third round. Williams won the title in 2002, 2003, 2009, 2010 and 2012.
''I don't know how I did it,'' Cornet said. ''Just with my heart -- and the help of the crowd.''
The No. 1-ranked and No. 1-seeded Williams owns 17 Grand Slam titles, one fewer than Martina Navratilova and Chris Evert, but she now has departed before the quarterfinals at four of the past five majors. There were fourth-round losses at Wimbledon last year and at the Australian Open in January, and a second-round loss at the French Open in May.
''Australia, I just couldn't play. And Paris I played really bad. Here, I actually thought I played better,'' she said. ''I'm going to have to watch this film.''
Cornet also beat the 32-year-old American at the Dubai Championships in February. Still, this result was rather unexpected, given their Grand Slam careers. Cornet never had been past the third round at Wimbledon, and she only once before reached a major's fourth round, in 2009.
Saturday's match was halted in the third game because of rain. After a delay of about 4½ hours, Williams was terrific, reeling off five games to grab the first set.
Things changed dramatically. Cornet began putting shots right where she wanted them, while Williams had trouble finding the mark. Williams wound up with 29 unforced errors, 11 more than Cornet.
''She helped me a little bit,'' Cornet said.
Two particular strokes troubled Williams: Her serve let her down repeatedly, with a total of seven double-faults and five breaks; her backhand produced 12 unforced errors.
In the third set, Cornet led 5-2 but was broken serving for the match. On her second chance, she steadied herself, delivering a perfect drop shot on match point.
When Williams netted the response, Cornet pounded her chest with her fist. Then she hopped around Court 1, before kneeling to kiss the grass.
Cornet had been 0-13 against top-20 opponents in Grand Slam matches.
''I don't really know what I did wrong,'' said Williams, whose sister Venus lost Friday. ''Usually I do. Usually I know I did this, this, and that.''
It was by far the most significant -- and surprising -- outcome on a wet day full of starts and stops.Three other past Wimbledon champions won on Centre Court, where the roof was closed and soccer star David Beckham was in the Royal Box: Rafael Nadal, Roger Federer and Maria Sharapova.
For his third match in a row this year at Wimbledon, two-time champion Nadal dropped the first set before coming back to win, this time beating 63rd-ranked Mikhail Kukushkin of Kazakhstan 6-7 (4), 6-1, 6-1, 6-1.
''From the very first points of the second set, he improved a lot. All his shots just started to be much more hard, powerful and more aggressive,'' Kukushkin said. ''It was like a different player.''
Sharapova, the 2004 champion, was up next in the main stadium, and she, too, overcame a slow start. But after falling behind 3-1, she won 11 consecutive games for a 6-3, 6-0 victory over 44th-ranked Alison Riske of the United States.
As for Federer, who has collected seven of his 17 major trophies at the All England Club, there really was never any trouble spot. He needed less than 75 minutes to eliminate 35th-ranked Santiago Giraldo of Colombia 6-3, 6-1, 6-3 and hasn't lost a set through three matches.
Nadal next faces 19-year-old Australian Nick Kyrgios; Federer meets No. 23 Tommy Robredo of Spain, who beat 2013 semifinalist Jerzy Janowicz of Poland 6-2, 6-4, 6-7 (5), 4-6, 6-3; and No. 8 Milos Raonic, only the second Canadian man in the Open era to get to Wimbledon's fourth round, plays either No. 10 Kei Nishikori of Japan or unseeded Simone Bolelli of Italy, whose match was suspended because of darkness at 3-all in the fifth set.
''It shows all of you who asked me if I'm ready to play Serena in Round 4,'' Bouchard said. ''That's one of the reasons I don't look far ahead.''