Kim Clijsters has pulled out of next week's Madrid Open because her left foot injury isn't healing fast enough. The latest scan on her foot confirmed two tears sustained during last week's Fed Cup victory over Estonia, forcing her to postpone her return to the tour and further threatening her participation in the French Open. The U.S. Open champion had counted on a quick recovery and a full clay-court preparation campaign ahead of the May 23 start at Roland Garros. Even though her foot felt better, Clijsters said in was not healing fast enough. Her doctor has said a full recovery could take up to six weeks.