LONDON — For 34 matches over 4½ months, on hard, clay, or grass courts, Serena Williams was unbeaten — and, in the minds of many, unbeatable.
So it was apt, somehow, that the longest winning streak in women’s tennis since 2000 would end at this memorably unpredictable edition of Wimbledon, where up is down, where seedings and pedigree mean nothing whatsoever, and where even five-time champion Williams looked lost.
Stumbling on the Centre Court grass a couple of times while her game slumped in crunch time, the No. 1-ranked and No. 1-seeded Williams dropped the last four games to bow out, 6-2, 1-6, 6-4, Monday against 23d-seeded Sabine Lisicki of Germany.
‘‘Didn’t play the big points good enough,’’ said Williams, who had won three of the past four Grand Slam titles, including Wimbledon a year ago and the French Open less than a month ago. ‘‘I didn’t do what I do best.’’
Oddly passive down the stretch, Williams essentially let Lisicki to do what she does best in their fourth-round match: dictate points quickly with a big serve, powerful returns, and pinpoint groundstrokes. If that sounds familiar, it could be because it’s the formula Williams uses to dominate her sport.
‘‘Come on, guys, let’s get with it. She’s excellent,’’ a composed Williams said at her news conference after blowing leads of 3-0 and 4-2 in the third set. ‘‘She’s not a pushover.’’
Especially at Wimbledon. Lisicki’s game is built for grass. She is a mediocre 16-15 at the other three Grand Slam tournaments and 17-4 at the All England Club. She reached the semifinals at Wimbledon in 2011, and is into her fourth quarterfinal, coincidentally beating the reigning French Open champion every time: Svetlana Kuznetsova in 2009, Li Na in 2011, Maria Sharapova in 2012, and Williams in 2013.
‘‘Obviously,’’ Lisicki said, ‘‘I went into the match feeling that I could win.’’
Might have been the only person who felt that way. After all, Williams owns 16 major championships, and entering Monday, the 31-year-old American had won 46 of 48 matches this season, and 77 of 80 since the start of Wimbledon in 2012.
The inevitability of failure, even for the most successful player, has never been made clearer than during this tournament. This was only the first day of the fortnight’s second week, yet Williams joined quite a list of those already gone: Roger Federer, Rafael Nadal, Victoria Azarenka, and Sharapova — all major title winners, all former No. 1s, all out by the end of Day 3.
Late Monday afternoon, British bookmakers were making Lisicki the favorite to win a trophy that hours earlier seemed destined for Williams. Asked whether that affects her in any way, Lisicki shot back: ‘‘No, not at all.’’ Not even a little bit? Lisicki didn’t blink and answered, ‘‘No.’’
It was the same steely demeanor the quick-with-a-smile Lisicki displayed at key moments on court, weathering a near-collapse in which Williams grabbed nine consecutive games to take the second set and go up, 3-0, in the third.
Williams hadn’t lost a match since her three-set defeat against Azarenka in the final of the Qatar Open Feb. 17. But Lisicki showed things would be different Monday with an early five-game run, including when she smacked a forehand return winner to break at love and take the opening set.
Lisicki yelled, ‘‘Come on!’’ The crowd, eager to see something special, roared. Williams walked to the sideline slowly, stunned.
‘‘I just was thinking, ‘Let’s get to a third set,’ ’’ Williams said. ‘‘That’s what I always say when I lose a first set.’’
Going from considerable trouble to total control, as if simply by wishing to do so, Williams produced 43 masterful minutes in which Lisicki did not win a single game. Williams did not have an unforced error in the second set, and she even got some unneeded assistance early in the third, with two consecutive return winners that both clipped the net tape and bounced over.
‘‘I felt,’’ Williams said, ‘‘that I was on the verge of winning.’’
Lisicki finally ended the drought by holding to 3-1 with one of her four second-serve aces in the match, then a 115-mile-per-hour service winner.
‘‘Huge serves,’’ Williams said. ‘‘Constantly, constantly, back-to-back-to-back.’’
That’s how her opponents usually feel. But Lisicki managed to get better reads on returns late, and broke to get within 4-3 with a forehand passing winner as Williams lost her footing and fell to her knees.
The next game was key. Lisicki fell behind love-40, meaning Williams had three break points, any of which would give her a 5-3 lead and allow her to serve for the match.
But Lisicki wouldn’t fold.
Suddenly serving for the biggest win of her career, Lisicki double-faulted to give Williams a break point — and an opening. But it was Lisicki who closed strongly, hitting a 113-.m.p.h. ace and a 99-m.p.h. service winner, and then ending a 17-stroke exchange with a forehand winner.