United close out the Premier League season with matches against Southampton and Crystal Palace.
"But like this I never have". And in the last 16 I was out only once.
"I don't want to think about it in this moment".
"It has been an incredibly busy season, which will see us play 64 matches including an astonishing nine matches last month".
Mourinho told Sky Sports that Tottenham had more to play for in their final game at White Hart Lane on Sunday.
He added: "And on top of that, the accumulation of big injuries - not small, not the injuries that you say "OK, hamstring, two weeks" - no, it's surgery, boom, boom".
"I don't know other clubs, the way they think or what is important for them", he said.
Although United have already won the League Cup and also face Ajax in the Europa League final on Wednesday week, some observers, including Roy Keane, feel United's Premier League campaign has been "embarrassing".
Jose Mourinho made no secret of his prioritisation of the upcoming Europa League final following Sunday's defeat against Tottenham, but his side are on offer at 9/5 (2.80) to bounce straight back from that result with a first league victory in five matches.
"In the league we set a new club Premier League record with 25 matches unbeaten within a single season".
"And I repeat the same - thank you Michael Oliver because we were out in the FA Cup, because if we go to the FA Cup semi-finals it would be a total disaster".
"We wanted to win the game, we went out and tried to win the game".
"The players who needed the rest got the rest". Winning that competition carries entry into the Champions League group stages.
"Even the draw [for the fixtures], if it is a draw, I never understood well if it is a draw", Mourinho said.
Having missed out on a top-four place in the league, United must beat Ajax to qualify for next season's Champions League.
Mourinho has openly admitted that domestic matters are little more than "compulsory", as he prepares his side for a Europa League showdown against Ajax on May 24.
"Blind played [against Tottenham] after 90 minutes on Thursday, of course Fellaini has to play the next because he is not playing now".