The Red Devils visit the La Liga outfit in the Champions League on Tuesday on matchday two of the league phase.
Michael Carrick’s side got off to a winning return at Europe’s top table, beating minnows Sabah 4-0 at Old Trafford last time out.
Now, they have been handed an additional boost, with centre-back De Ligt returning after almost a year out with a back problem that he picked up against Crystal Palace.
Caution will be taken over the Dutchman, who travelled with his team-mates to Fulham before the international break, but he did not make the matchday squad.
Return: Matthijs de Ligt
PA
Belief was building at Carrington when he featured in a behind-closed-doors friendly against sister club Lausanne-Sport, and now, the club have confirmed that he will be part of the squad that converges on the Estadio Metropolitano.
United have been dealt a double injury blow in the build-up to the game, with Kobbie Mainoo and Luke Shaw left at home.
Carrick confirmed on Monday evening that the pair had picked up knocks in the 1-1 draw with Tottenham, and as such, they would both be ruled out of the trip to the Spanish capital.
United are sat in 12th in the Premier League after a stuttering start to the campaign, and scrutiny only intensified on Carrick after Dominic Solanke’s late equaliser at Old Trafford salvaged a share of the spoils for Roberto De Zerbi’s ten men.