Arsenal boss Mikel Arteta admits Thomas Partey faces several weeks out.
The Ghana midfielder is facing more scans today.
Arteta confirmed: "He's got a muscle injury and we expect him to be out for a few weeks. We don't know the extent of it still, he has more tests today. He got that injury in training, with the last kick of the ball. Very unfortunate."
Arteta was asked if the injury was suffered while Partey was with Ghana.
He replied: "I don't think so. He was coming from a period of absence and he needed minutes. He played with the national team. We try to be in touch with them always. Then we had two games very close with Chelsea and Seville.
"We decided not to load him in Chelsea and play him in Seville, and then it happened in training. So, sometimes it's difficult. We try to prevent it. If he had got injured against Chelsea or against City you would have said we rushed him. And then we don't and he gets injured. It happens. That's football."