Coco Gauff crashed out of Wimbledon on a day of significant first-round shocks but defending champion Barbora Krejcikova kept her nerve to battle back from a set down.

US second seed Gauff came to the All England Club with high hopes after winning the French Open last month but was beaten 7-6 (7/3), 6-1 by Ukranian world number 42 Dayana Yastremska.

Other high-profile casualties on day two of the grass-court Grand Slam were women's third seed Jessica Pegula and fifth seed Zheng Qinwen.

Instead of building on her success on the Paris clay, 21-year-old Gauff endured her earliest Grand Slam exit since another first-round loss at Wimbledon in 2023.

The two-time Grand Slam champion paid the price for an unusually error-strewn display featuring nine double-faults, 29 unforced errors and just six winners.

Earlier, US Open runner-up Pegula suffered a shock defeat against Italy's Elisabetta Cocciaretto, losing 6-2, 6-3 in just 58 minutes.

Pegula was followed out of the tournament by Olympic champion Zheng, who went down 7-5, 4-6, 6-1 against unheralded Katerina Siniakova.

But Zheng's compatriot, Wang Xinyu cruised past the 15th seeded Karolina Muchova in straight sets 7-5, 6-2.

The 23-year-old built on the fine form she exhibited at the Berlin Open, where she reached her first WTA Tour final by defeating four top-20 players in a row.

In the men's draw, third seed Alexander Zverev bowed out of the tournament, beaten in five sets by French world number 72 Arthur Rinderknech, giving a bleak assessment of his state of mind after the match.

The German, who reached the Australian Open final earlier this year, suffered his earliest Grand Slam exit since 2019 after a marathon match that started on Monday evening.

Afterwards he made surprisingly frank comments, saying he was considering therapy to talk through his mental health issues.

"It's funny, I feel very alone out there at times," he said. "I struggle mentally. I've been saying that since after the Australian Open." (AFP/Xinhua)