Having been a part of Tottenham's youth set-up during their playing days, Carrick and McKenna worked together at Old Trafford under Jose Mourinho, taking the reigns for a temporary stint after he was sacked.
They remained with the Red Devils while Ole Gunnar Solskjaer was in charge, but left to begin their own coaching careers shortly after his departure.
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Carrick came in as Boro boss in October 2022, replacing Chris Wilder after Leo Percovich's interim spell in charge. He guided them to a fourth-place finish, with the likes of Chuba Akpom and Cameron Archer firing them into the play-offs, where they were beaten by Coventry City.
They finished eighth in the following campaign and 10th last season, ending with a miserable run of one win, one draw and four defeats to ensure another season in the second tier.
As a result, Middlesbrough have now opted to part company with Carrick, alongside assistants Jonathan Woodgate and Graeme Carrick.
Kieran McKenna worked with Carrick at Manchester UnitedKieran McKenna worked with Carrick at Manchester United (Image: PA)
Speaking about his relationship with the former England midfielder back in December 2023, McKenna said: “He was certainly higher up in the echelons than me [as a player in Spurs' academy].
“When he first came into Tottenham, he actually spent some time in the reserves under Jacques Santini, I think.
“We spent some time in the reserves, and he obviously got promoted to the first team pretty quickly and showed the quality that he had at Tottenham. Of course, he went on to have a fantastic career.
“I’ve known him for a long time. He’s someone I hold in the highest regard as a player, a coach, and most importantly as a person.
“I had a good relationship with him, even as youth team coach [at Manchester United]. He had a couple of injuries, so he spent some time training with us even. He was a fantastic role model, even then.
“We have very similar views on things, on football, how we like the game to be played. There’s quite a lot of things that we enjoy from a tactical point of view and similarities in how we want our teams to go about things.
“We share quite a lot of viewpoints. I’ve learned and benefited a lot from the relationship in football.”