United sit five points above Arsenal in the table ahead of Sunday's visit to Emirates Stadium, while the Gunners have a game in hand in the fight for a top-four finish.
However, a 1-0 win at Celta Vigo on Thursday put one United foot in the Europa League final and winning Europe's secondary competition will guarantee a place in the Champions League next term.
Having taken charge of nine matches in April, and with one eye on United's semi-final second leg at Old Trafford next Thursday, Mourinho will make changes to his tired squad.
He said: "The players that will play in accumulation and the players that are with a lot of minutes – because we played nine matches in April and this one, so 10 matches in four and half weeks – the players that are in accumulation will not play next weekend."
Marcus Rashford limped off after scoring the only goal of the game at Balaidos with a curling free-kick, while Ashley Young also departed with an apparent hamstring injury 11 minutes after coming on.
With Luke Shaw, Zlatan Ibrahimovic and Marcos Rojo out for the season, Mourinho's options have thinned considerably for the run-in.
Rashford's form has been a recent positive for Mourinho, with vital goals in Europe against Anderlecht and Celta helping fill the void left by Ibrahimovic.
"He worked really hard and he was creating problems," Mourinho said of the England international.
"He had a fantastic shot in the first half with that beautiful save and then the free-kick is work. He works every day, he loves to work.
"Sometimes the training session will finish for the group and he keeps doing individual work with my assistant so the free-kick is really well taken. I think the goalkeeper has no chance because it was a really fast goal."