SANTA CLARA, Calif. -- The San Francisco 49ers were on the practice field, executing their game plan to stop the Indianapolis Colts' offense when events in the Midwest immediately altered their work.In a rare, in-season blockbuster trade, the Colts acquired running back Trent Richardson from the Cleveland Browns for a first-round pick next year. The Colts made the trade because they had a weakened ground game after losing running back Vick Ballard to a knee injury.