Hanson, a second-round pick in 1992, opted to retire when a contract agreement couldn't be reached with the Lions for the 2013 season. Hanson said he didn't want to play for another team.
No player in NFL history has played more games with one team (327). The 42-year-old is the NFL-record holder with 52 field goals of 50-plus yards and is third all-time with 2,150 points and 495 field goals.
The Lions could sign his replacement soon or wait to find a rookie during or after the draft. The Ravens signed undrafted kicker Justin Tucker before 2012, and he made multiple game-winning kicks for the Super Bowl champions.
Former San Francisco 49ers kicker David Akers visited the facility this week and at least one other free agent, Justin Medlock, worked out for the Lions.