Defending champion Elena Rybakina made the Wimbledon quarter-finals on Monday after opponent Beatriz Haddad Maia quit in tears with injury after just five games.
Rybakina was 3-1 up when Brazilian world number 13 Haddad Maia took a medical timeout on Centre Court to treat a lower back injury.
She limped back onto the court but was reduced to walking pace and was in tears as she saw out the fifth game before retiring.
"It's never easy to finish a match like this. I hope it is nothing really serious, it is really unlucky for Beatriz," said Rybakina.
"Hopefully she is going to get better and I am just happy to play another round."
She added: "I was feeling the ball really well even though it was really windy today."
World number three Rybakina will face either two-time champion Petra Kvitova or 2022 runner-up Ons Jabeur for a place in the semi-finals.
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