At the age of nine, Clijsters began working with Benny Vanhoudt in the more distant town of Diest. Along with her sister, she trained for fifteen hours a week, including five hours of individual instruction, which Vanhoudt said was "an insane amount total hours." She continued to train in Diest until she was twelve. During this time, she also first worked with Carl Maes and Wim Fissette, both of whom would coach Clijsters later in her professional career. When she was thirteen, Maes took over as her primary coach at the Flemish Tennis Association in Antwerp.