The Red Devils have seen their resources tested to the full this season as they have competed in four competitions until their FA Cup elimination last month.
A 0-0 draw at home to West Brom on Saturday – an eighth stalemate of the season at Old Trafford – leaves United five points off Man City in fourth and six behind Liverpool in third, albeit with games in hand.
They also have the option of focusing on their Europa League quest as a possible route back to European football’s top table, with Mourinho conceding that some tough selection calls lie ahead.
The Portuguese said after watching his team toil against the Baggies: “I just want to think that against Everton [on Tuesday] we are going to do what we tried to do against West Brom, to try to play with our best team and try to win the match.
“And after Everton we go to Sunderland with the same perspective. And then after Sunderland the Europa League comes, and then I don’t know.
“Then, it’s possible that you see me play in the Premier League with a team where I’m going to protect the players that I consider fundamental for the Europa League.
“But only if the results in the next matches put us in a situation where, mathematically, it becomes almost impossible to do it.”
United are due to face Anderlecht at the quarter-final stage of the Europa League, with the first leg on Thursday April 13.