Tuesday 25 November 2014 17:09, UK
Jack Wilshere is facing more time on the sidelines after injuring his ankle during Saturday's defeat to Manchester United.
The Arsenal midfielder is to see a specialist after a late challenge from United defender Paddy McNair forced him off before the end of the 2-1 defeat at the Emirates.
Wilshere will be out "for a while", according to Arsene Wenger, who does at least have defender Laurent Koscielny back in his squad for Wednesday's Champions League game against Borussia Dortmund.
"I cannot give you any time schedule," Wenger said. "We don't know at the moment. He has a big ankle sprain and I don't want to talk about it because I am not a specialist medically.
"The first news is they have told us that he will be out for the next few games. To find out for how long, we will need to see a specialist."
Koscielny has been battling a persistent Achilles problem and has been out since Arsenal lost at Chelsea at the beginning of October.
In the absence of the France centre-half and his compatriot Mathieu Debuchy Arsenal's makeshift defence has struggled, conceding seven goals in the past three matches, and another cornerstone of the regular back five will be missing against Dortmund.
Goalkeeper Wojciech Szczesny collided with team-mate Kieran Gibbs during the United game and is ruled out, leaving Emi Martinez to start an Arsenal game for just the second time.
Olivier Giroud, who was not registered for the Champions League group stage after breaking his leg in August, is ineligible, but Danny Welbeck is in the squad despite missing training on Tuesday.
Arsenal will qualify for the knockout stage for the 15th year in succession if they avoid defeat at the Emirates.
Watch Arsenal v Borussia Dortmund live on Sky Sports 1 from 7.30pm on Wednesday.