Key posted the news on his Twitter account.
Key, a junior, was one of the SEC's top pass-rushers in his three seasons at LSU. He had 17 sacks in his first two seasons, but his 2017 campaign disrupted by injuries.
He is currently No. 16 overall on Mel Kiper Jr.'s Big Board, projected as a potential first-round pick.
The 6-foot-6, 265-pound Key had four sacks in eight games this season and did not play in the Citrus Bowl presented by Overton's. Key also did not participate in spring football before his junior season while taking a leave of absence from the team.
His ability when healthy has rarely been questioned, given his production and physical gifts, making him an appealing draft prospect for NFL teams. He was an SEC All-Freshman team selection in 2015 and was a first-team Associated Press All-SEC selection as a sophomore.