The Red Devils and the Rojiblancos have both been out of sorts this season, and likely view European salvation as their final lifeline - and with the scores tied after a 1-1 first leg in Spain, it will be a winner-takes-all encounter at the Theatre of Dreams.
Fernandes is in the worst form of his Manchester United career and Marcus Rashford is struggling badly.
Meanwhile the visitors are taking the fouls that are on offer and doing everything else they can to just turn this into a bit of a grindfest, killing the momentum and frustrating the crowd.