Mikel Arteta was forced to leave Wednesday's Champions League match after the Arsenal midfielder suffered a calf injury in the second half against Borussia Dortmund.
Arsene Wenger: "[Mikel] Arteta doesn't look good. It's a calf injury; he'll be out for a while. These injuries are very difficult to take."
— Squawka Football (@Squawka) November 26, 2014
The injury forced the Spaniard to leave the match in the 67th minute, with Mathieu Flamini brought in to replace him.
Arteta was the second Arsenal player to leave the match through injury as forward Yaya Sanogo left the game with a hamstring ailment.