The Minnesota Vikings placed safety Harrison Smith on injured reserve/designated to return and signed cornerback Jacob Lacey on Friday.
Smith, who has a turf toe injury, can return to practice in six weeks and be activated in eight weeks.
Smith was injured in the fourth quarter of Sunday's loss to the Carolina Panthers.
Losing Smith is a serious blow to the Vikings' lagging secondary, with depth issues at almost every position.
A first-round pick in 2012, Smith has become the Vikings' best defensive back and is expected to be replaced by special teamer Andrew Sendejo.