Jockey David Clark, who recently picked up his 2,500th win, will be sidelined four to six weeks with a fractured wrist.The veteran rider who began his career in 1973 was injured after a horse he was aboard tried to jump a fence during a morning workout on Thursday."David came off the horse and stuck out his hands to help break his fall," said Clark's agent Ken Zweig. "He fractured his right wrist in a couple of places and it will require surgery."Two years ago, the 50-year-old Clark came back to enjoy a solid meet after missing two months of action because of a morning training accident. Through June 17, Clark is the Toronto oval's second leading rider, winning 28 races and recording $1.35 million in purse earnings.