But both players could well be involved from the start against Brighton, with Mourinho suggesting that, following a full weeks' worth of training, the duo are in better condition to feature.
He told the club's official website: “I think we will have the same players [as against Leicester]. I think the injured players aren’t going to be back for Brighton.
"What we have is Paul [Pogba] with nine days' training, [Marcus] Rashford with 11 days' training, [Marouane] Fellaini with nine days' training and, of course, they will be in a better condition.
"Normally, these boys that [against Leicester] were in a difficult situation will be ready to give a bit more [against Brighton] – more Lukaku, more Rashford, probably Lingard coming back, more Fellaini. I think normally we’re going to have more."
That means that United will still be without the likes of Nemanja Matic and Antonio Valencia, while Ander Herrera and Marcos Rojo will also miss out having also been absent from the win over Leicester.
The Red Devils will be looking to build on the opening-day victory over Claude Puel's men, with Paul Pogba's penalty and Luke Shaw's first ever goal for the club ensuring they came out with a 2-1 win.
After facing Brighton, United take on Totenham at Old Trafford on August 27 before a trip to Burnley on September 1.