By agreeing to sign with the Lions, Leggett will get to once again play for defensive coordinator Gunther Cunningham. Originally signed by the Kansas City Chiefs as an undrafted free agent from Valdosta State in 2008 (Cunningham's last year in Kansas City), Leggett was named the Chiefs' best rookie that year. He had 37 tackles, six pass defenses and one interception (returned for a touchdown) in 12 games and played very well for an undrafted free agent.
Leggett's stats dropped a bit in 2009 because of a shoulder injury. He had his season ended early due to it, and last year he had his season ended before it even began due to a injury.
Leggett seems like he could be a decent player if he can stay healthy. Based on suffering injuries each of the last two seasons, that is obviously a big question mark, but this seems like it could be a low risk, high reward type of move.