The Lions re-signed Vildor to a one-year contract Wednesday.
Vildor was absent from the Lions' injury report Tuesday after he left Sunday's loss to the Bears early with cramping.
Vildor is questionable to return to Sunday's contest with the Bears due to cramping issues.
The Bears waived Vildor on Tuesday, Patrick Finley of the Chicago Sun-Times reports.
Vildor ended the season with 34 tackles and an interception over 11 games.
The Bears placed Vildor (ankle) on injured reserve Friday, Larry Mayer of the team's official site reports.
Vildor (ankle) is listed as out for Saturday's game versus the Bills.
Vildor (ankle) didn't practice Wednesday.
Vildor (ankle) is active for Sunday's game versus the Eagles.
Vildor (ankle) was a full participant at practice Wednesday ahead of Sunday's game versus Philadelphia.