WIMBLEDON, England — When Petra Kvitova won a warmup tournament in Birmingham, England, last month, a successful run at Wimbledon seemed an enticing possibility.

A two-time champion at the All England Club, Kvitova had missed months of action after her left hand was slashed in a terrifying encounter when an intruder broke into her home in the Czech Republic. She came back ahead of schedule to play in the French Open, but Wimbledon, where she has performed so well, had been her real target.

But on Wednesday, Kvitova, the No. 11 seed, was crouched over, sweat pouring from her forehead as she gasped for air in the third set. Exhausted and overwhelmed, she succumbed in the second round, 6-3, 1-6, 6-2, to Madison Brengle, an American ranked 95th.

Kvitova said she had trouble breathing and felt sick at times. She also said she was not certain her problems stemmed from a lack of conditioning after missing half a year of time on court.

“Who knows, maybe,” she said, adding, “It happened at Wimbledon, which is not nice.”

Venus Williams, now the only former Wimbledon champion left in the women’s draw, struggled on Wednesday as well. The No. 10 seed, Williams overcame a poor first set to beat Wang Qiang, 4-6, 6-4, 6-1.

On the men’s side, top-seeded Andy Murray showed no signs of the aching hip that had hampered him before the tournament. He easily dismissed his friend Dustin Brown, 6-3, 6-2, 6-2, in their second-round match, and at the net, Brown acknowledged that Murray took him to school.

Murray followed his fellow British player Johanna Konta, the No. 6 seed in the women’s draw, on Centre Court. Konta needed 3 hours, 10 minutes to shake off Donna Vekic of Croatia, 7-6 (4), 4-6, 10-8. The final set took 1:19.

No. 13 Jelena Ostapenko, the surprise French Open champion, narrowly avoided joining the list of vanquished seeds when she came from behind to beat Françoise Abanda of Canada, 4-6, 7-6 (4), 6-3.

Victoria Azarenka, playing in her first Grand Slam tournament since giving birth to her son in December, beat No. 15 Elena Vesnina, 6-3, 6-3.

In the last match on Centre Court, fourth-seeded Rafael Nadal, the French Open champion, beat Donald Young, 6-4, 6-2, 7-5.