In Wednesday's 0-0 draw at Southampton he again selected an understrength XI, omitting Marcus Rashford, Michael Carrick, Ander Herrera, Paul Pogba and David de Gea.
Southampton, beaten 3-2 by United in the League Cup final at Wembley in February, have now won just one of their last eight home games in all competitions while United stretched their winless league run to five.
Sergio Romero has spent the majority of his Manchester United career living in the shadow of David de Gea, but has thanked Jose Mourinho for allowing him to take centre stage in next week's Europa League final.
"In any country in the world the match would be Saturday, because Sunday we are sixth, doesn't matter what, and Crystal Palace are safe", said Mourinho. They are phenomenal. And I keep saying the Portuguese kid [Pereira] is a very good goalkeeper.
Jose Mourinho confirmed after the match that he intends to use the same policy in the remaining two Premier league matches, especially considering that United can not even dream about a top four finish.
That news did little to quell rumours of De Gea's imminent departure, with his appearance against Tottenham last time out possibly his final in a United shirt, but Mourinho moved quickly to confirm the Spaniard is still firmly in his plans.
Southampton manager Claude Puel refused to discuss his future at the club, which is the subject of speculation. Both Phil Jones and Chris Smalling are in line to start, as they continue to rebuild their fitness ahead of the Europa League final. "I am happy for the second half because we played good football with good chances to win the game which is important for us".
Southampton's Dusan Tadic, centre, in action against Manchester United's Marouane Fellaini, right, and Anthony Martial during an English Premier League soccer match at St Mary's, Southampton, England, Wednesday, May 17, 2017.
"I hope not", he smiled when asked of the possible bruising.
"He's gone from this very charismatic guy to very dour, and I think it's to do with the size and scale of the Manchester United job - that brings its own set of pressures".
"Fellani hasn't got a tear but he's experienced enough to know he had a feeling".
"Sometimes it's hard and sometimes it's easier but the players are all battling and improving to work for him".