Defending champ Garbine Muguruza upset by Alison Van Uytvanck

LONDON -- Defending champion Garbine Muguruza is out of Wimbledon in the second round, leaving only two of the top-eight-seeded women still in the field after only four days of action at the All England Club.

Muguruza, the No. 3 seed, was stunned 5-7, 6-2, 6-1 by 47th-ranked Alison Van Uytvanck of Belgium, who entered this year's edition of Wimbledon with a 1-4 record in the grass-court tournament.

Muguruza joined No. 2 Caroline Wozniacki, No. 4 Sloane Stephens, No. 5 Elina Svitolina, No. 6 Caroline Garcia and No. 8 Petra Kvitova on the way out so far, along with five-time major champion Maria Sharapova.

"I mean, anyone, on a good day, can beat anyone,'' Van Uytvanck said. "That's what I think. I still think the top players, their average level is higher than, let's say, sub-top players. But anyone on a good day can beat anyone, for sure.''

Muguruza had not only won her second career Grand Slam title in 2017 at Wimbledon but also reached the 2015 final. Her other Grand Slam win came in the 2016 French Open.

"It's a little bit sad,'' Muguruza said. "But today didn't go my way.''

In other women's matches, former Wimbledon finalist Angelique Kerber had to come from a set down to oust American qualifier Claire Liu in the second round.

The 11th-seeded Kerber broke decisively for a 4-3 lead in the third set before serving out a 3-6, 6-2, 6-4 victory against the 18-year-old Liu, the youngest player in the tournament.

Kerber lost the 2016 final to Serena Williams.

Liu was at her first Wimbledon and faced a top-10-ranked player for the first time. At No. 237, Liu was the lowest-ranked woman to make the second round.

Top-ranked Simona Halep won the last 10 games to beat Saisai Zheng of China 7-5, 6-0 on Thursday.

Saisai led 5-3 in the first set, but Halep broke back for 5-5 and cruised the rest of the way against her 126th-ranked opponent.

Halep won her first Grand Slam title at the French Open this year. She lost in the quarterfinals at Wimbledon in 2016 and 2017.

No. 7 Karolina Pliskova is the other top-eight-seeded woman left in the draw.

Eugenie Bouchard of Canada, who lost to Kvitova in the 2014 Wimbledon final, lost to 17th-seeded Ashleigh Barty 6-4, 7-5.

The Associated Press contributed to this report.