Kvitova felt the injury to her right hamstring following her first-round win over Lucie Safarova at the Eastbourne tournament in England. She played her second-round match against American Varvara Lepchenko.
But on Thursday, she withdrew from the tournament.
Kvitova says she is uncertain of the full extent of the injury but will get treatment and expects to play at Wimbledon next week.
She says “I hope that just some days off will help.”
Kvitova is the No. 6 seed at Wimbledon.
Almagro was No. 25 in the men’s seedings, so Wimbledon officials shuffled the rankings ahead of Monday’s opening matches.
Canada’s Vasek Pospisil was placed the seedings at No. 31, while other players moved up.
Wimbledon’s draw will be held Friday. Novak Djokovic and Serena Williams were No. 1 seeds.
Contributing: Associated Press
