United make three changes from the first leg as Phil Jones, Jesse Lingard and Anthony Martial replace Luke Shaw, Diogo Dalot and Romelu Lukaku.
That means it could be Jones at full-back for United unless they are playing with a back three.
Alexis Sanchez, who hasn’t played since March 2 due to injury, could face his former side as he is on the bench.
ROBERTO REPLACES SEMEDO
Barcelona make just one change from the first leg, having rested nearly all of their first-team regulars, including Lionel Messi and Luis Suarez, at the weekend.
Suarez, Messi and Philippe Coutinho start as the front three again while Sergio Roberto replaces Nelson Semedo at left-back.