United are preparing for their semi-final first leg against Celta Vigo on Thursday (4 May) and have been decimated by injuries in recent weeks, though Mourinho will be able to call upon Paul Pogba, Phil Jones and Chris Smalling for the clash at the Estadio Municipal de Balaidos.
Despite the positive news on the injury front - a rarity for Manchester United in recent weeks - Mourinho's squad is still being pushed to its limit.
The Portuguese concedes that his side's priority is to achieve Europa League glory rather than reach the top four in the Premier League, and is not afraid to rest some of his star players against Arsenal - a side he has never lost to in that league - as he bids to find a way past Celta.
"I think it would be a good achievement, given the problems, and to allow us to be back to Champions League next season we are going to try, and the Europa League becomes for us now more important," the Manchester United boss said in his pre-match press conference.
"Of course it depends on the result [against Celta], how we analyse the game. But if we have to rest players next weekend [against Arsenal] then we are going to do that. In relation to the Premier League I think it's too late, because in the past month we played nine matches, seven of them in the Premier League.
"We had too many problems [with] too many players and, because of that, players who have to play 750 and 800 minutes of football, and we paid the price. We played against fresh teams and we were in [a period of] accumulation."
Along with Pogba, Smalling and Jones, Mourinho will also be able to call upon defender Eric Bailly against Celta Vigo and Arsenal. The Ivory Coast international seemed to suffer a hamstring problem during United's draw against Swansea City on Sunday but has been passed fit to play. The same can't be said of Luke Shaw, whose season is now over due to a foot problem suffered against the Swans.