McKenna was a youth footballer at Tottenham Hotspur, before he ended his playing career in 2009, due to a hip injury; he went through two years of rehabilitation and had two operations performed before confirming his decision to hang up his boots, his body no longer stable to play professional football. Prior to that, he played for Ennskillen Town United and Ballinamallard United. Furthermore, he represented Northern Ireland at both under-19 and under-21 level; he represented his country of birth at the UEFA European Under-21 Championship Qualifiers.
Coaching career
Tottenham Hotspur
After retiring, McKenna took up a career in coaching, and in 2015 was placed in charge of Tottenham Hotspur's under-18 side, having previously been coaching a variety of teams within their Academy set-up. McKenna revealed that he almost joined the coaching staff at Liverpool, where he would have replaced Alex Inglethorpe, who had been promoted from coach to academy director. He stayed one day at Liverpool's Melwood training complex, in preparation to sign a contract with the Merseyside club, though decided to remain at Tottenham. During his tenure at Tottenham, McKenna was able to guide the under-18s to the semi-finals of the FA Youth Cup just months into his position. He departed just a year after his appointment with the under-18s, having accepted the opportunity to serve the same role for their Premier League rivals Manchester United.
Manchester United
In his second season in charge of the under-18s, McKenna guided Manchester United to the Premier League Northern Division title. Having served as their under-18s coach for the past two seasons, on 1 July 2018, along with former United player Michael Carrick, he replaced Rui Faria as Jose Mourinho's assistant manager, ahead of the forthcoming Premier League season. Mourinho left United on 18 December 2018, and was replaced the next day by club legend Ole Gunnar Solskjær, who was appointed as caretaker manager. Despite reporters suggesting that the managerial change would result in the recruitment of a new coaching team, both McKenna and Carrick were able to keep their positions under Solskjær, and were joined by Mike Phelan, a heavily respected coach who had previously served as United's assistant manager under Sir Alex Ferguson.
Reception
Following his arrival at Manchester United's under-18s as their new manager, Indy Boonen, who was a teenage player for United at the time, praised McKenna, stating, "He changed everything. The way we trained was how the opponent played on the Saturday. If you played against West Brom, you trained how they are and focused on their weaknesses." Jim Magilton, the Irish Football Association's elite performance director, agreed with Boonen's appraisal of McKenna, commenting, "He is a meticulous planner yet every session is spontaneous. Nothing is set in stone. He adjusts the session to how the players are and gets what he wants out of the session. Everything is linked and game related. Nothing is for show – it has to be about the game." After claims that McKenna's coaching methods "lacked continental expertise", Manchester United supporters backed the coach, with them believing that McKenna is one of the greatest young coaches in England. It was claimed that players were not convinced about McKenna's coaching, though manager Ole Gunnar Solskjær and fellow assistant coach Michael Carrick trust him. United insiders, employed by The Times, stated, "McKenna to be one of the best young coaches in England – and one who will only get better. He helps on the pre-match preparations, determined to get United the best possible chance of tactically outclassing their opposition. And McKenna reportedly spends every plane or coach journey going over footage of matches, pouring over data and relaying it to his superiors."
Personal life
Since his childhood, McKenna has been a supporter of Manchester United, with reporters claiming that his love for the club had persuaded his decision to leave Tottenham Hotspur for the Red Devils in 2016.
