Arsene Wenger had this to say:
"He is limping quite badly and has a sprained ankle. He's a strong boy, so I still hope he will recover. But it looks to me like he could be short for Wednesday. It's a big game for us on Wednesday as well, because the team want to do well in the Champions League.
"It's a long way to travel. But it's simple - if there's a risk I won't take it. But if the medical staff say he can play I will play him."
"Samuel looked as though he didn't want to hurt Vieira on purpose, even though he had a high leg."