Richardson played two snaps against Dallas before leaving the game for good when Cowboys defensive end George Selvie stepped on his foot on the Rams' third play from scrimmage.
Leading into Sunday's game, Richardson had already been dealing with a foot injury that ailed him since the opener against Arizona. Last week, Richardson did not practice Wednesday but was listed as a full participant on Thursday and Friday.
Richardson didn't get a carry before Selvie aggravated the injury.
"It's a little [frustrating] but you have got to just keep praying and treating it because when it's time to go, you've got to be ready to go," Richardson said Monday night.
Richardson won the starting job in the preseason and leads the team in carries (30) and yards (98) through the first three weeks. Despite his status as "limited" Monday, Richardson insisted he'd be ready to go when the Rams play San Francisco on Thursday night.
"I'm good to go for Thursday," Richardson said.