Arsenal will be without both their captain and vice-captain against Albion in the FA Cup at The Amex tomorrow.
Thomas Vermaelen picked up an ankle injury when he clashed with team-mate Aaron Ramsey as they went for the same ball in Wednesday's 5-1 Premier League win against West Ham at The Emirates.
Mikel Arteta has been out with a calf tear and Arsene Wenger confirmed this morning both players will miss the fourth round tie, together with Francis Coquelin (hamstring).
Tomas Rosicky, who has been out with a calf strain, returns to the Gunners squad with Abou Diaby, who missed the West Ham match due to illness.
An extra 500 tickets for the match, made available to home supporters by Albion, sold out within 40 minutes this morning.