The Real Madrid loanee had been struggling with an ankle issue and was limited to a cameo role in the 1-0 Premier League defeat against Everton last week, but gets the nod from the off in Spain in a boost to Mikel Arteta.
Captain Pierre-Emerick Aubameyang and centre-back David Luiz are deemed fit enough for the bench tonight, but there is no Kieran Tierney or Alexandre Lacazette, despite the duo training in advance of the match.
Nicolas Pepe looks to be leading the line with no Lacazette and Aubameyang - who has now recovered from malaria - only a sub.
Granit Xhaka looks poised to continue at left-back, meanwhile.
Villarreal’s starting XI includes Tottenham loanee Juan Foyth, with ex-Gunners midfielder Francis Coquelin on the bench.
Villarreal XI: Rulli, Pedraza, Pau, Albiol, Foyth, Parejo, Capoue, Trigueros, Alcacer, Chukwueze, Moreno
Subs: Sergio Asenjo, Mario, Funes Mori, Bacca, Estupinan, Moreno, Coquelin, Jaume, Moi Gomez, Pino, Baena, Nino
Arsenal XI: Leno, Chambers, Holding, Mari, Xhaka, Partey, Ceballos, Saka, Odegaard, Smith Rowe, Pepe
Subs: Bellerin, Gabriel, Willian, Aubameyang, Cedric, Luiz, Nelson, Elneny, Nketiah, Ryan, Martinelli, Okonkwo