Former assistant head coach Steve Agnew has joined Aston Villa as first team coach.
Agnew, who had two spells at the club, and had rejoined Boro three years ago as assistant head coach to Aitor Karanka, said: "I want to express my appreciation to everyone at MFC - particularly Steve Gibson and all the supporters.
"The club, the area, and the people will always mean a great deal to me personally. However, it's time to move forward and on to a new, exciting challenge with Aston Villa and working with Steve Bruce again."
The club would like to wish Steve the best of his luck in his new role.