The tie is wide open after the first leg which ended 0-0 at the Ramon Sanchez Pizjuan, but Sevilla's defeat to Valencia at the weekend makes Mourinho's side the slight favourites.
And that's just how Jose Mourinho likes it.
Young, 32, is just six games away from equalling his highest number of appearances in a season for United, having made 27 so far this term in comparison to the 33 he racked up during his first campaign at Old Trafford in 2011-12.
But Mourinho, who has won the competition twice before with Porto and Inter Milan, said United will start "smelling" the semi-finals if they manage to get past Sevilla.
Marcus Rashford talks through his two goals in Man United's 2-1 win over Liverpool and the patience required in making his return to Jose Mourinho's XI.
Mourinho confirmed £89 million (S$162.4 million) club-record signing Paul Pogba trained yesterday, having missed their 2-1 win over Liverpool on Saturday with a gashed leg, but Ander Herrera, Marcos Rojo, Daley Blind and Phil Jones look set to miss out. "And I remember him clearly in the meetings in the dressing room, at halftime, eating every word, listening to everything".
Rashford has played less since the turn of the year than before, with his role becoming more that of a substitute than a starter, but his double against Liverpool will change that. Rashford has experienced the kind of inconsistency many his age show but the 20-year-old offered a timely reminder of his brilliance against Liverpool to also prove to Mourinho he can be relied upon in the big moments.
Antonio Valencia is nearly certain to keep his place at right-back while I expect Ashley Young to once again start ahead of Luke Shaw on the left. "It was a wonderful solution and the fans reacted against the kid".
McTominay stands out on the field.
Against Liverpool, he formed an impenetrable midfield block with Nemamja Matic, helping United to keep its shape against Liverpool's fluid attack. Those players could well be the future of United and deliver when called upon.
Mourinho agrees and it will be fascinating to see how McTominay develops at United in the coming years.
With Carrick announcing his retirement on Monday as well as his aspiration to feature in the final few matches of the season, it would take a heart of stone to not even include him in the squad.
The former England global also indicated there is a good chance he will remain on the bench next season, albeit in a coaching role.