Arsenal had two players substituted due to injury on Wednesday Prmeier Leage clash against Manchester United.
Rob Holding and Aaron Ramsey were forced off before the second half of their clash with United at Old Trafford.
Ramsey was back in the Arsenal starting line-up after his inspirational second-half cameo helped drive them to victory in the North London derby against Tottenham on Sunday.
His display sparked talk of the club reviving contract talks after he had appeared certain to leave the club when his current deal expires in the summer.
But he is now potentially facing a spell on the sidelines after being unable to play through the ankle injury sustained at Old Trafford.
Holding 23, was replaced by Stephan Lichtsteiner after 36 minutes of the clash with Marcus Rashford which saw the England under 23 defender stretcher off after appearing to injure his left knee.
Medics checked him over on the side of the pitch before the decision was made for Unai Emery to replace him.