Jockey Mark Johnston, who last week passed the 3,000 wins mark, fractured his wrist Saturday afternoon at Delaware Park. He broke the radius bone in his left wrist when Mt. Moran stumbled at the gate and tossed him."The doctor set the bone yesterday and said it was a good place to break it," said Johnston. "I should be back on a horse in two weeks and expect to make my return on Oct. 8 when the Laurel Park fall meet opens."Last Thursday at Pimlico, Johnston became the 102nd rider in history to ride 3,000 winners. This year Johnston is 31st in the nation with 159 victories and earnings of just under $4 million. The 1990 Eclipse Award winning apprentice has at least 200 wins for eight consecutive years.