WIMBLEDON, England — The two-time Wimbledon champion Petra Kvitova was stunned in the first round on Tuesday, losing by Aliaksandra Sasnovich, 6-4, 4-6, 6-0.
Kvitova was seeded eighth and among the leading favorites at the All England Club. She was coming off a grass-court title at Birmingham, England, last month and entered Tuesday with a tour-leading 38 victories this season.
Sasnovich, ranked 50th, came in with a 2-3 career record at Wimbledon, including a first-round loss a year ago, and a 9-13 Grand Slam mark.
Kvitova was one of four top-10 women and men to fall Tuesday after No. 4 Sloane Stephens, No. 5 Elina Svitolina and No. 6 Grigor Dimitrov lost Monday.
Sixth-seeded Caroline Garcia exited the singles draw about 90 minutes after Kvitova, losing to the former top-10 player Belinda Bencic, 7-6 (2), 6-3.
On the men’s side, seventh-seeded Dominic Thiem, the French Open runner-up last month, he retired hurt with his opponent, Marcos Baghdatis, leading by 6-4, 7-5, 2-0.
Thiem received a medical timeout for treatment on his back, before the pain eventually became too much early in the third set.
Reaching the final at Roland Garros was a career-best Grand Slam result for the 24-year-old Austrian, but the grind of the clay-court season appeared to have taken its toll.
Matthew Ebden upset 10th-seeded David Goffin of Belgium, 6-4, 6-3, 6-4. The 51st-ranked Ebden had lost all three of his previous meetings with Goffin, but needed only 1 hour 33 minutes to earn his first win over a top-10 ranked player at a Grand Slam event. Ebden, a 30-year-old Australian, has never been past the second round at a major.
Things were much smoother for top-seeded Simona Halep and the defending women’s champion Garbiñe Muguruza.
Halep eased into the second round with a 6-2, 6-4 win over Kurumi Nara of Japan in 78 minutes. Halep, the French Open champion, was playing her first match since winning her first Grand Slam title at Roland Garros but showed no signs of rust.
After losing just one set on her way to the Wimbledon title a year ago, Muguruza picked up exactly where she left off at the All England Club.
The No. 3-seeded Muguruza was hardly troubled in beating the British wild card Naomi Broady, 6-2, 7-5.
Muguruza failed to build upon her dominant display at last year’s Wimbledon as she exited the United States Open in the second round and this year’s Australian Open in the fourth.
But her best tennis — and both of her Grand Slam titles — have come during the European summer, and a run to the French Open semifinals last month suggests that may be the case once more.
Only an inspired performance from the eventual champion Halep knocked her out at Roland Garros, and with grass being better suited to Muguruza, she is a major contender at Wimbledon.
“The fact that it’s different surfaces, it helps,” Muguruza said.
Her next opponent will be the unseeded Alison Van Uytvanck of Belgium.
Johanna Konta, who knocked out Halep en route to the semifinals a year ago, made it through to the second round by defeating Natalia Vikhlyantseva of Russia, 7-5, 7-6 (7).
Angelique Kerber won a first-round meeting of former Wimbledon runners-up, beating Vera Zvonareva, 7-5, 6-3. Kerber lost the 2016 final to Serena Williams, who also beat Zvonareva in the 2010 title match.
Zvonareva was playing in her first Grand Slam tournament in three years after a hiatus to get married and have a child. She came through three rounds of qualifying to make the main draw at the All England Club.
The Australian trio Daria Gavrilova, Ashleigh Barty and Samantha Stosur all advanced with straightforward wins.
The 26th-seeded Gavrilova cruised past the American lucky loser Caroline Dolehide, 6-2, 6-3. She will face Stosur in the next round, after she defeated Shuai Peng of China, 6-4, 7-5.
The 17th-seeded Barty defeated her Swiss opponent Stefanie Voegele, 7-5, 6-3, to claim her first main-draw singles victory at the All England Club. She will next face Eugenie Bouchard, the 2014 runner-up here.
On the men’s side, second-seeded Rafael Nadal moved into the second round with a 6-3, 6-3, 6-2 win over Dudi Sela of Israel.
Nadal had not played a match since claiming his 11th French Open title last month, but showed little sign of rust as he cruised to victory against Sela.
Nadal is seeking a first Wimbledon title since 2010, which would also make him just the second man to do the French Open-Wimbledon double three times.
Juan Martín del Potro maintained his record of never losing in the first round at Wimbledon with a 6-3, 6-4, 6-3 win over Peter Gojowczyk of Germany.
The fifth-seeded Argentine will next face Feliciano Lopez, who broke Roger Federer’s record by appearing in a 66th consecutive Grand Slam singles tournament as he defeated Federico Delbonis of Argentina, 6-3, 6-4, 6-2.
Fourth-seeded Alexander Zverev was also through after defeating James Duckworth of Australia, 7-5, 6-2, 6-0.
No. 15 seed Nick Kyrgios hit 42 aces and saved all five break points he faced to beat Denis Istomin of Uzbekistan, 7-6 (3), 7-6 (4), 6-7 (5), 6-3. Kyrgios earned the only break of the match to go 5-3 up in the fourth set before serving out the match.