The midfielder suffered a fractured ankle in the FA Cup win over Portsmouth last time out and will be sidelined for some time.
Tomas Soucek has made a rapid recovery from injury to be fit for West Ham.
The Czech midfielder suffered a hip injury against Liverpool a fortnight ago but is already back in contention.
Provisional Arsenal squad: Leno, Martinez, Bellerin, Papastathopoulos, Luiz, Mustafi, Mari, Holding, Tierney, Saka, Maitland-Niles, Guendouzi, Xhaka, Willock, Ceballos, Ozil, Pepe, Nelson, Lacazette, Martinelli, Nketiah, Aubameyang.
West Ham provisional squad: Fabianski, Ngakia, Diop, Ogbonna, Cresswell, Rice, Noble, Fornals, Bowen, Antonio, Haller, Randolph, Zabaleta, Balbuena, Masuaku, Snodgrass, Soucek, Lanzini, Anderson.