Trent Richardson will not participate in the Combine due to minor knee surgery he had three weeks ago. No information on the type of surgery, but it was done to relieve discomfort from an injury he sustained before the BCS game. He will likely miss Alabama's Pro Day on March 7.
It's possible he can try to hold his own Pro Day in early April. It shouldn't cause him to drop much in the draft, but it may be a little more likely he can slip out of the top 10 if teams can't see him go through the drills.