“He was doing another test and obviously he felt something muscular,” said Mikel Arteta.
“But he’s been much, much better and they’ve both been really well. So we’ll make the decision this afternoon on what we’ll do.”
The forward is, however, available for selection and Arteta insisted on Wednesday everything had been resolved with him after holding talks.
There could be further changes to the side, with Mohamed Elneny pushing to come in for fellow midfielder Thomas Partey and Hector Bellerin hoping to start at right-back.
Arsenal predicted lineup (4-2-3-1): Leno; Bellerin, Luiz, Gabriel, Tierney; Elneny, Xhaka; Pepe, Odegaard, Smith Rowe; Aubameyang.
Thursday 5.55pm GMT, BT Sport
Referee: Carlos del Cerro Grande
Arsenal squad from: Leno, Ryan; Bellerin, Cedric, Chambers, Gabriel, Holding, Luiz, Mari, Tierney; Ceballos, Elneny, Odegaard, Partey, Saka, Smith Rowe, Xhaka; Aubameyang, Balogun, Lacazette, Martinelli, Nelson, Nketiah, Pepe, Willian.
Injury doubt: Saka (hamstring)