Seattle announced the trade on Sunday. The Seahawks had an open spot on their 90-man roster after releasing defensive tackle Tony McDaniel in a salary cap move. The draft pick going back to Detroit is expected to be a late-round selection.
Seisay appeared in 13 games last season for Detroit as a rookie, and played in the Lions' playoff loss to Dallas. Seisay was signed by the Lions as an undrafted rookie free agent out of Nebraska.
Seisay fits the profile of Seattle's cornerbacks at 6-foot-2 and 200 pounds. Two projected contributors in Seattle's secondary -- Jeremy Lane and Tharold Simon -- are both still recovering from offseason surgeries.