Smith, who was among the team's final pre-season cuts, started 10-games for the Lions in 2010, leading Detroit corners with five interceptions and 27 tackles.
Detroit was weak at cornerback following a concussion suffered by Jacob Lacey and a shoulder injury to 2012 third-round draft pick Bill Bentley in Detroit's 26-23 overtime win over the Philadelphia Eagles Sunday.
Williams, a third year running back, rushed for 195 yards and two touchdowns for the Lions in 2011, but had just two carries and two receptions this season.
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