With the Red Devils up 1-0 after the first leg, Mourinho will hope to see his side finish the job and advance to the final on May 24 in Solna, Sweden.
In total, there are eight changes from the team which lost 2-0 to Arsenal in the Premier League on Sunday, with the bench also identical to the one which helped to secure the win in Vigo last week save for Phil Jones stepping in for the injured Ashley Young.
With Zlatan Ibrahimovic, Marcos Rojo and Luke Shaw also out with season-ending injuries, the XI chosen by the Portuguese represents his strongest available line-up. That backs up his claims in recent weeks that the Europa League is now United's number one target despite them retaining an outside hope of qualifying for the Champions League through finishing in the top four of the Premier League.
United are looking to win the Europa League in any of its guises for the first time in their history.
Man Utd XI: Romero, Valencia, Bailly, Blind, Darmian, Ander Herrera, Fellaini, Lingard, Pogba, Mkhitaryan, Rashford
Subs: De Gea, Smalling, Jones, Carrick, Mata, Martial, Rooney
Celta XI: Sergio, Mallo, Radoja, Pablo Hernandez, Guidetti, Iago Aspas, Sisto, Wass, Jonny, Cabral, Roncaglia.
Subs: Villar, Fontas, Diaz, Bongonda, Beauvue, Jozabed, Sergi Gomez.