The Premier League side face off against the Vincenzo Montella's in-form La Liga outfit at the Ramon Sanchez Pizjuan for the first-leg fixture, which Mourinho claims United aren't favourites for.
While downplaying expectations from the away fixture, the Portuguese tactician claims the defensive-minded approach from his Italian counterpart may not create the goal-fest fans have been demanding in recent weeks.
"With Sevilla, I don't think it's possible to score many goals," he told MUTV. "I think the game is going to be really competitive.
"They can say what they want; they can be nice to us and say we are favourites - that means absolutely nothing. For me, the word 'favourite' or 'not favourite' means nothing.
"They have good defensive organisation; they defend with everybody. Montella is Italian and Italian coaches know how to organise their teams very compact from the defensive point of view."