Richardson gained 44 yards on 11 carries and added 16 yards on two catches in Friday's 30-17 preseason loss to the Lions.
The 26-year-old tailback built on his impressive training camp performances, with his 44 yards leading all rushers on the night. Richardson has not received a regular-season carry since 2013, his second and final season with the Rams. He's competing with Fitzgerald Touissant for a third-string role behind DeAngelo Williams, with Friday's effort serving as a positive step towards winning that job.