BRUSSELS — Kim Clijsters is out for up to six weeks after tearing a muscle in her left foot during a Fed Cup singles match against Estonia.

Clijsters beat Maret Ani 6-4, 6-2 Saturday despite discomfort in the foot. The bruising got more painful overnight, forcing her to pull out of Sunday's second match. Tests at a hospital showed the muscle tear in her foot.

She will use crutches for a few days to give her foot a chance to heal. It was unclear when she could resume full training.

The French Open at Roland Garros starts in four weeks, on May 23, and Clijsters is hoping that intensive treatment will shorten the six-week rehabilitation period.

Justine Henin replaced her for Sunday's match against Kaia Kanepi.

Henin broke her left pinkie during training on Wednesday and had not been slated to play singles this weekend even though she is right-handed and plays with a single-handed backhand. She made herself available because of Clijsters' injury.