Richardson now is the second-string back with a reduced workload, Silver said.
"It's a bottom-line biz," a source told NFL Media Insider Ian Rapoport regarding Richardson's demotion. "Change needed to be made. Donald is our most productive guy."
Brown has displayed more explosiveness and an ability to create creases, whereas Richardson has been stymied.
According to Rapoport, the Colts still believe in Richardson's future, but, with playoff positioning on the line, they need to ride the hot hand.
Silver added that offensive coordinator Pep Hamilton is under pressure within the Colts' facility to "step up his game" after the offense got off to slow starts in the past several weeks. According to two sources, there a feeling that Hamilton might be having a tough time adjusting in his first season as an NFL play-caller.
According to Silver, there is a belief that the team has struggled to free up receivers in the wake of Reggie Wayne's injury. The play-calling might get more imaginative and aggressive this week to combat the bracket coverage T.Y. Hilton is facing.