As we await Ruben Amorim's selection for the 20:00 BST kick-off, there, is of course, your chance to get involved in our popular United Predictions game.
We have garnered opinion from our pundits and reporters in advance of the first leg at San Mames - see if you agree with what they are saying...
ADAM MARSHALL:
United XI: Onana; Yoro, Maguire, Shaw; Mazraoui, Ugarte, Casemiro, Dorgu; Fernandes (c), Garnacho; Hojlund.
First scorer: Alejandro Garnacho.
Final score: 2-2.
Man of the Match: Alejandro Garnacho.