Serena Williams pulled out of the French Open before her fourth-round match with Maria Sharapova on Monday, while Rafael Nadal moved into the quarter-finals with a straight-set victory over Germany's Maximilian Marterer.
Serena, the 23-time Grand Slam winner recently returned to tennis after giving birth to her first child, but had to call off her comeback because of an injury that affected her serve.
"I've had issues with the right pectoral muscle to the point where I can't serve," said the 36-year-old.
"I'll have a scan. I won't know about Wimbledon until I get the results."
Williams said she first felt the problem during her third-round win over German 11th seed Julia Gorges on Saturday, according to a BBC report.
Elsewhere, ten-time French Open champion Nadal beat Marterer 6-3 6-2 7-6 (7-4) to seal the spot in the quarter-finals for a 12th time.
The 32-year-old Spaniard lost his opening service game and trailed 2-0 in the first set in Paris before recovering well.
He broke Marterer's serve early in the second set and fought back from 3-1 down in the third for a straight-set win against the unseeded 22-year-old.
Nadal will play 11th seed Diego Schwartzman, 25, in the last eight.
The Argentine recovered from two sets down to beat South African sixth seed Kevin Anderson 1-6 2-6 7-5 7-6 (7-0) 6-2 to move into the second Grand Slam quarter-final of his career - and first at Roland Garros.
His compatriot Juan Martin del Potro also moved into the last eight with a 6-4 6-4 6-4 win over American ninth seed John Isner.
He will play third seed Marin Cilic, who overcame Italian 18th seed Fabio Fognini 6-4 6-1 3-6 6-7 (4-7) 6-3. The Croat had led by two sets before his opponent played some brilliant tennis, particularly in the tie-break, to draw level.
However, Cilic, who has never progressed beyond the last eight at Roland Garros, broke his opponent in the fifth game of the final set before going on to seal victory.
