The two clubs are vying for a spot in the showpiece event against either Manchester United or Roma, and here Sports Mole rounds up all of the latest team news ahead of the first leg.
Out: Vicente Iborra (knee)
Sports Mole's predicted XI: Asenjo; Foyth, Albiol, Torres, Estupinan; Chukwueze, Parejo, Capoue, Trigueros; Moreno, Alcacer
Doubtful: Kieran Tierney (knee)
Sports Mole's predicted XI: Leno; Chambers, Holding, Gabriel, Xhaka; Partey, Ceballos; Saka, Odegaard, Pepe; Lacazette