It’s a tricky test too as Barca go into the game 1-0 down and have plenty of work to do if they are to book their place in the last four.
As such Ernesto Valverde is likely to go for a very strong team. Let’s have a look at how they might line up.
Jasper Cillessen is Barca’s Copa del Rey goalkeeper and should continue between the sticks.
In front of him it’s a straight choice between Nelson Semedo and Sergi Roberto at right-back. Thomas Vermaelen is injured so we should see Gerard Pique and Samuel Umtiti at centre-back and possibly Yerry Mina on the bench.
Valverde also has to choose between Lucas Digne and Jordi Alba at left-back, but given Barca’s predicament, expect the Spain international to get the nod.
Valverde has rotated his midfield in this tournament but we can probably expect his strongest midfield four. Andres Iniesta has been back in training so hopefully will be fit, and will join Ivan Rakitic, Sergio Busquets and Paulinho.
Interestingly, Philippe Coutinho could be fit enough to make the squad. Will Valverde throw him in from the start? That remains to be seen but he might get his Barcelona debut at some point on Thursday night.
Barca need to score goals to win this tie and with Lionel Messi and Luis Suarez both in brilliant form, Valverde simply has to go with his star forwards.
Paco Alcacer has been spotted in training, but it’s not quite clear if he’s match fit yet, while Jose Arnaiz has been a hit in this competition and could make the bench.
Possible starting XI: Cillessen; Semedo, Pique, Umtiti, Alba; Rakitic, Busquets, Paulinho, Iniesta; Messi, Suarez.
How should Barca should line up against Espanyol? Let us know your thoughts and line-ups in the comments below!