However, if he did face the axe, some names are likely to come to the fore as potential successors. We take a look at five early favourites.
At the moment, Zinedine Zidane looks like the most obvious choice for the Red Devils were they to cut ties with Mourinho. The Frenchman is still fresh from winning nine titles in two and a half years in charge of Real Madrid. Zidane cannot really be classified as a master tactician in the mould of Pep Guardiola, but what he has proven to be is a brilliant man-manager. He took a collection of individual talents and egos at Real and brought the best out of them to achieve unprecedented success.
In many ways, that could be said to be what United need – a manager who can take talented individuals and get all of them performing at a high level. Zizou probably would struggle to plug the leaky Red Devils’ defence, but he would definitely bring back an attacking ethos to the club. Crucially, he is available and would not cost United a dime.
Tottenham Hotspur boss Mauricio Pochettino enhanced his credentials as Mourinho potential’s successor by leading his side to a 3-0 win at Old Trafford on Monday night. In four years, the Argentine has transformed Spurs from a team striving to break into the Champions League, to one that is now perceived as a potential title contender season in, season out.
Pochettino’s ability to develop and trust in young players would be highly appreciated at Old Trafford. The one thing that might act as a small red flag is his apparent disdain of particular trophies, despite having never won one as manager yet. It would also be incredibly difficult to prise him from the hands of Spurs and their notoriously tough negotiator chairman Daniel Levy.
Diego Simeone has particular traits that would be very attractive to United. Above his competitiveness and track record of success, he has proven his loyalty and longevity by spending nearly eight years at Atletico Madrid. In that time, he has consistently punched above his weight to deliver two Europa League trophies, one La Liga title and one Copa del Rey trophy. He has also reached two Champions League finals.
Simeone is similar to Mourinho in the sense that he builds his teams primarily on a strong defensive foundation, which probably makes him a less attractive prospect than Zidane or Pochettino. He might be an easier target to land than Pochettino is at the moment, but it is difficult to see him abandoning Atletico in the middle of a season.
Ryan Giggs has already tasted life in the hot seat at Old Trafford. He was appointed interim manager when Moyes was sacked with four games to go to the end of the 2013/14 season. The Welshman, who represented United for more than two decades as a player and coach, is now in charge of the Wales national team.
It is hard to see him abandoning his tenure with Wales barely one year since his appointment. If he took over the reins, it would probably be on a short-term basis again.
If United are looking for a ready-made manager with a proven track record and can compete for success, Antonio Conte could be the answer to their problems. In many ways, such an appointment would mirror their appointment of Mourinho two years ago, but Conte would probably be seen as less of a liability especially from a PR perspective.
The former Chelsea and Juventus boss could help to stabilise things in defence for United, given that he demonstrated an ability to instil discipline in his previous jobs. He particularly demonstrated his tactical prowess whilst restructuring his Chelsea side to a three-man defence two seasons ago, a change that triggered a 13-game winning run for the Blues on the way to the title.