Charleston, USA, 5 April 2013 | AP/AAP

A recurring calf injury has forced Sam Stosur to retire from her third round match at the WTA Family Circle Cup in Charleston.

Third-seeded Stosur was trailing 6-1 2-0 against Canadian qualifier Eugenie Bouchard when she called it quits.

“It’s unfortunate for Sam. Hopefully she’ll be better soon,” Bouchard said after booking a quarterfinal against former world No.1 Jelena Jankovic.

Stosur, who turned 29 last Saturday and won the 2010 Charleston title, first suffered the injury at Indian Wells last month.

The lingering injury is a concern just two weeks before Australia’s Fed Cup World Group playoff in Switzerland and six weeks before the start of the French Open.