The Brazilian suffered an ankle injury in Sunday's win over Sheffield United.
"We don't know. He was in pain the other day when he had to leave the pitch," said Arteta.
"He's not a player that normally does that, so he was uncomfortable.
"We assessed him yesterday and he was a bit better, but we don't know. He had a scan this morning as well to see how bad it is and he's very willing.
"He wants to play but he's always like that. We will have to see how he is."