It means the three-time continental champions will this season ply their trade in the Europa League, getting their first ever group stage campaign under way on Thursday with a tough-looking trip to Eredivisie leaders Feyenoord.
Mourinho has played 125 Champions League and Super Cup fixtures since his last dalliance with the competition, when he led Porto to UEFA Cup glory against Celtic in 2003.
It is clear that the Portuguese, his players and the club would rather not be in the Europa League, but the manager is attempting to change the mindset as United try to win the only major continental trophy missing from their cabinet.
“Look, this is not a competition that Man United wants,” Mourinho said on the eve of the match in Holland.
“It is not the competition I want, it is not the competition the player want, but it is a competition where we are and that’s the reality.
“We have to look to the competition with respect. I think we want to do well in the competition and for a club of our dimension to do well is not to be out of the competition in the group phase.
“I know the group phase is not easy. I know that the group phase could be perfectly a Champions League group phase with clubs that fight for the title like Fenerbahce, Feyenoord and Man United, but this is the competition where we are.
“I think you can see by our selection of players – apart from Luke Shaw, Antonio Valencia and Wayne Rooney – that we come to come to respect the opponent and we come to win the game. We want to win the competition.
“It is difficult to do it but it is simple to feel it and say it, and this is the way we want to approach the competition.
“Tomorrow is an important match for us and we must find that motivation that I have found myself already.
“I have to try to pass that motivation to the players because I know that the Europa League is not the big dream of every big player.
“But you are not in the Champions League, so you have to find your motivation in the competition where you are.”
Mourinho highlighted February’s embarrassing last-32 loss at FC Midtjylland as what can happen if you sleep walk into a Europa League tie, making him determined to emit the “right message”.
World-record signing Paul Pogba and Zlatan Ibrahimovic, who has not played in the competition since 2001, are part of that show of strength in Rotterdam, where Shaw, Valencia and Rooney are the key absentees.
The latter’s omission raised eyebrows after featuring so heavily under Mourinho, but is borne out of the desire to have the United captain ready for Sunday’s return to Premier League action at Watford.
“He plays every game since the beginning of the season, he played also 90 minutes for England, he played 90 minutes last weekend,” Mourinho said. “I want him to be fresh for the next Premier League match.
“At the same time, it is a kind of attacking position where he is playing where I have lots of solutions in the attacking position and people that are working hard to have a chance.”