Leeds United manager Jesse Marsch has paid tribute to former coach Mark Jackson after he was named new MK Dons manager.
The 45-year-old has replaced Liam Manning at the League One club in what is his first senior managerial role.
Jackson worked in Leeds' academy for seven years before Jesse Marsch promoted him to first-team coach at the end of last season.
Marsch said about his departing assistant: "His passion, commitment and love of this club made him essential for me and us in our quest to stay in the league.
"I fully believe that without him that we wouldn't have stayed in the league. He has been outstanding during my time at Leeds and he will be sadly missed."
Marsch will now look for a new coach for his backroom staff as Leeds director of football Victor Orta added: "Not only has Jacko been instrumental in progressing many of our young players, but he has also been a really important part of Jesse's team."
MK Dons are third bottom of League One and Jackson said: "I'm ready for the challenge. It is clear what the short-term targets are, but I want to help build something special in the long term as well."