LONDON — Madison Brengle knew, of course, that her opponent, Petra Kvitova, was a two-time Wimbledon champion and a popular pick to win the title again this year.

Brengle also was aware, of course, that she herself never had won so much as one main-draw match at the All England Club until this week.

This, instead, is all the 27-year-old from Dover, Delaware, was focused on as she began playing Kvitova on Wednesday evening on Court No. 2: Please just let me win a game. The 95th-ranked Brengle did just that – and much, much more, stunning the 11th-seeded Kvitova 6-3, 1-6, 6-2 to reach the third round at Wimbledon.

The reason for Brengle’s preoccupation with taking merely a single game? In her Wimbledon debut in 2015, she lost to Venus Williams 6-0, 6-0.

“So, like, that’s always in my head when I’m out here,” Brengle said, pointing a finger at her right temple. “It’s like, ‘Oh, my goodness, don’t do that ever again!’ That was really tough for me.”

Turned out, she didn’t need to stress about a shutout for too long: Brengle broke the strong-serving Kvitova to take the very first game.

“As long as I got on the board to start, then I could relax,” Brengle said with a smile, “because, trust me, an ‘O-and-O’ stays with you.”

Now she’ll have this victory to cherish, along with another one from this year that holds some significance: Brengle beat Serena Williams at a tuneup tournament at Auckland, New Zealand, back on Jan. 4. Williams went on to win the Australian Open that month and hasn’t played since – she is pregnant and taking at least the rest of this year off – so Brengle is, for the moment, the last woman to defeat the 23-time Grand Slam champion.

“That’s my thing,” Brengle said, holding up a fist and laughing. “I’m going to hold on to that one forever.”

Kvitova, who won Wimbledon in 2011 and 2014, had been favored by some British bookmakers to lift the trophy at fortnight’s end, despite competing in only her third tournament of her comeback. She was attacked by a knife-wielding intruder at her home in the Czech Republic in December and needed surgery on her left hand, the one she uses to hold a racket.

Kvitova was one of a half-dozen seeded women to lose on Day 3, a group that also included No. 15 Elina Vesnina (beaten by new mom Victoria Azarenka, a former No. 1 and two-time Australian Open champion), No. 17 Madison Keys, No. 18 Anastasija Sevastova, No. 22 Barbora Strycova and No. 25 Carla Suarez Navarro.

The action was much more straightforward in the men’s draw, with straight-set victories by defending champion Andy Murray and Rafael Nadal, who has won the last 26 Grand Slam sets he has played.

For Keys, the 6-4, 6-7 (10), 6-1 exit in the second round against 86th-ranked Camila Giorgi of Italy was the American’s earliest in five appearances at the All England Club.

“The whole time, I was just kind of waiting for her level to drop and it never really did,” said Keys, who recently had a second surgery on her left wrist to remove scar tissue from the original procedure in October.