Arsenal recently announced their Europa League main squad list, following the official deadline for submission a couple of weeks ago. However, they can still make changes to the B-list up until a few days before each matchday.
To briefly explain, the B-list is specifically reserved for under-21 players who have been at their club for two full years. You also have to have a professional contract with the club. Anyone on the B-list can feature in senior Europa League matches.
For example, Joel Lopez is eligible after his move from Barcelona in 2018. But Omar Rekik isn’t, given he only joined in January.
If you’re an u21 who hasn’t been at your club long enough, they can still play you as long as they have enough space to include you in the main squad list. That’s what Arsenal did with Gabriel Martinelli, who is ineligible for the B-list this season.
Arsenal have added three new u21s to the B-list this week, Brooke Norton-Cuffy, Alex Kirk, and Zach Awe. This is because they’ve all recently agreed professional deals with the Gunners, though we haven’t had official confirmation of Awe’s yet.
As well as those three, Tolaji Bola, Trae Coyle, Tom Smith, and Zak Swanson have all been added to the B-list after their loan spells ended.
Arsenal had to leave over-21 players Runar Alex Runarsson and Dejan Iliev out of the senior list, due to the restrictions on spaces.
Nikolaj Moller, George Lewis, Tim Akinola, Jonathan Dinzeyi, Omar Rekik, Catalin Cirjan, Salah-Eddine, Marcelo Flores, and Joel Ideho are all ineligible for the B-list, having been at Arsenal for less than two years.
Main Squad List
Goalkeepers: Bernd Leno, Mat Ryan, James Hillson
Defenders: Hector Bellerin, Gabriel Magalhaes, Rob Holding, Cedric Soares, Calum Chambers, Pablo Mari, David Luiz
Midfielders: Kieran Tierney, Dani Ceballos, Martin Odegaard, Willian, Thomas Partey, Mohamed Elneny, Granit Xhaka
Forwards: Alexandre Lacazette, Pierre-Emerick Aubameyang, Nicolas Pepe, Gabriel Martinelli
Goalkeepers: Karl Hein, Arthur Okonkwo, Tom Smith
Defenders: Tolaji Bola, Joel Lopez, Zak Swanson, Alex Kirk, Zach Awe, Zane Monlouis, Brooke Norton-Cuffy
Midfielders: Bukayo Saka, Emile Smith Rowe, Ryan Alebiosu, Ben Cottrell, Miguel Azeez, Omari Hutchinson, Charlie Patino
Forwards: Reiss Nelson, Eddie Nketiah, Folarin Balogun, Trae Coyle, Jordan McEneff
As a note, the positions given above are from the official UEFA website. Personally, I would swap Kieran Tierney to defenders, Jordan McEneff to midfielders, and Bukayo Saka to forwards, but what you see above is what UEFA provides.