The England international, who has been impressive for the Gunners of late, limped off with a hamstring injury in the 36th-minute of the 2-0 win at Southampton on Wednesday.
Following the game, Wenger said: "It's a hamstring problem. But we don't know how bad it is.
When asked if the 23-year-old could miss the FA Cup final against Chelsea, Wenger added: "I don't know. It doesn't look, because he walks properly. It was tight, it was not a knife, you know. Personally, I didn't see any incident where he had to stop for a sprint, it was more fatigue. But it's difficult to assess now, after the game."