Linebacker James Harrison is retiring from the NFL after a 15-season career.

Harrison announced Monday on Instagram that he's walking away from the game.

He signed with the Patriots on Dec. 26 after he was released by the Steelers, the team that signed him as an undrafted rookie in 2002.

After playing just 40 snaps over 14 games with Pittsburgh last season, Harrison immediately made an impact on the Patriots defense and was on the field for 69 snaps for New England in Super Bowl LII.

Harrison made his Patriots debut in week 17 against the Jets and recorded five tackles and two sacks.

Harrison spent 14 seasons with the Steelers and retires as the team's all-time leader in sacks with 80.5.