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. They think they can win now with a complete offense led by second-year quarterback Andrew Luck.

Expect the Colts to get Richardson involved in the offense right away. Richardson initially may not be as comfortable and as involved as he will be in coming weeks, but he will be able to play an immediate role. He may not see the field on some of the Colts’ more complicated plays, but he’ll get playing time against San Francisco.

The 49ers’ defensive coaches are altering their attack accordingly and boning up on Cleveland film as much as possible Wednesday night.