Collins, 28, has 19 carries for 49 yards and three touchdowns, along with 39 receptions for 174 yards and four touchdowns, in 47 career games.
The closest the Lions had to a fullback on their roster last season was Montell Owens, who played in just one game because of injuries.
Owens is only 5-10, 225 pounds, not your typical "fullback."
Collins is 6-1, 255.
He was brought in after Henry Hynoski visited the Lions’ headquarters last week but opted to re-sign with the New York Giants.
The Lions are expected to use more traditional two-back formations next season under their new coach Jim Caldwell and offensive coordinator Joe Lombardi.
This would mark the first time the Lions have a true fullback since 2010 when Jerome Felton (6-foot, 246 pounds) rushed for 76 yards on 22 carries and caught eight passes for 54 yards, with no touchdowns.