Three underwhelming years under firstly David Moyes and then Louis van Gaal saw the Old Trafford board turn to the Portuguese last summer.
EFL Cup and Community Shield triumphs in his first campaign have been tempered by Premier League struggles, with Sunday’s 1-1 draw against Swansea leaving United in fifth — a point shy of Manchester City with four tough fixtures remaining.
A trip to Arsenal awaits on Sunday and Mourinho could rotate his side given the match comes between European semi-final clashes against Celta Vigo, with Europa League glory offering Champions League qualification and a place in the history books.
Only Ajax, Bayern Munich, and Juventus have won all three major Uefa trophies, including the now-defunct European Cup Winners’ Cup, as well as the Club World Cup or the Intercontinental Cup.
United never tasted trophy success in the Uefa Cup, which evolved to become the Europa League from the 2009/10 season.
Mourinho said ahead of tonight’s first leg against Celta in Spain: “I know that it is the only competition that Manchester United as a club have never won and it would be great to close the circle and say: ‘We are a club that won every single competition in the football world’.
“Thinking about us as a team, I think it would be a good achievement and would allow us to be back to Champions League next season.
“So we have to try, that’s what we are going to do, and honestly the Europa League for us now becomes more important.
“Of course it depends on the result, it depends on the way we analyse the situation tomorrow after the match, but if we have to rest players next weekend, we are going to do that.”
Mourinho also revealed left-back Luke Shaw will miss the rest of the season with a foot injury.
“Luke Shaw is injured and it is an important injury obviously,” Mourinho said.
“But we are still waiting for one more medical opinion for the medical department to decide what to do.
“But it doesn’t matter what, he is out for the season. That is confirmed.”
For his part, Celta Vigo coach Eduardo Berizzo has called on his troops to be true to themselves.
He said: “How do you beat Manchester United? By being faithful to who we are.
“I think this team has a very clear identity, they know who they are and they believe in this identity: a lot of pressure, a lot of possession, recovering the ball quickly to attack again. The only way to beat Manchester United is to be faithful to who we are, facing such a great team.”