Arsenal goalkeeper Bernd Leno was stretchered off after suffering a potentially serious injury during the first half of his side's Premier League clash at Brighton on Saturday.
Leno screamed in pain after sliding awkwardly when he came to collect the ball just inside his own penalty area.
The German seemed to twist his knee and was given oxygen during several minutes of treatment on the pitch before being taken off.
Leno appeared frustrated with Brighton forward Neal Maupay, shouting and pointing a finger at him while being stretchered to the tunnel.
Maupay had been the Brighton player challenging Leno for the ball when he fell.
Already hit by injuries to Granit Xhaka and Pablo Mari in their 3-0 defeat at Manchester City on Wednesday, Leno's departure was another blow to Gunners boss Mikel Arteta.
Arteta was also missing Brazilian defender David Luiz, who was sent off against City.