Per Mertesacker fears his season could be over after damaging his ankle in Arsenal's 2-1 victory at Sunderland.
The central defender picked up the injury in first half at the Stadium of Light as James Mcclean opened the scoring for the Black Cats and he had to be stretchered off the pitch.
Mertesacker has now confessed on his Twitter account that the injury is not good but he will know more once he has undergone a scan on the problem later today.
"The foot is not good," he revealed. "I have to wait for the physical examination. Right now I'm living with uncertainty. Thanks for all your messages.
"Now off for scan. I fear the worst. Could miss the rest of the season."
The defender is certain to miss the game against AC Milan in the Champions League but he could be facing even longer on the sidelines if the injury is serious.
If the 27-year-old is ruled out then Wenger will go with Laurent Koscielny and Thomas Vermaelen at centre-back against AC Milan, with Kieran Gibbs returning at left back.