La Blaugrana prepare for the trip to the Basque region with five definite absentees in the form of Gavi (ACL), Raphinha (hamstring), Marcos Alonso (back), Marc-Andre ter Stegen (back) and Inigo Martinez (hamstring), while Joao Cancelo (knee) and Andreas Christensen (ankle) are both doubtful.
Neither man was able to take part in team training on Monday, despite previous optimism that Christensen's discomfort would clear up in time for the quarter-final, so at least one 17-year-old should be called upon here.
Pau Cubarsi earned plaudits for his performance against Real Betis on his La Liga debut over the weekend, but he appeared to be cramping up towards the end and gave way to Joao Felix in the 81st minute.
Cubarsi should be given the green light to take on Athletic, but with Xavi sure to avoid any risks with his growing body, his fellow La Masia product Hector Fort could be drafted into the backline instead.
With Fort operating on the right and Alejandro Balde skipping down the left, Ronald Araujo and Jules Kounde should form the barrier in front of Inaki Pena, with the Frenchman shifting infield from his right-back role.
Given the calibre of opposition, Pedri, Ilkay Gundogan and Frenkie de Jong are seemingly primed to link arms in the engine room once again, although Sergi Roberto and Oriol Romeu will provide fresh legs if necessary.
Hat-trick hero Ferran Torres and Robert Lewandowski should be final third shoo-ins, but Lamine Yamal - purely for fitness reasons - could potentially lose his place to Felix, who complemented Torres's treble against Betis with an exquisite outside-of-the-boot strike.
Barcelona possible starting lineup:
Pena; Fort, Kounde, Araujo, Balde; Pedri, Gundogan, De Jong; Torres, Lewandowski, Felix