"Right hamstring injury sustained during Emirates FA Cup semi-final on July 18".
Often a divisive figure among Arsenal supporters, Mustafi became an integral part of Arteta's side - starting all-but two of their last 14 Premier League games prior to his injury.
But despite his heroics at Wembley, Mustafi will not be returning for Saturday's showpiece against London rivals Chelsea.
Arsenal are set to be without a trio of centre-backs for the FA Cup final against Chelsea on Saturday evening.
"It looks really nasty", said the Spaniard of Mustafi. "Further assessments during the week identified a significant injury to the right hamstring", the club said in a statement. The latest team news released by Arsenal has revealed that Bellerin has returned to training with the rest of his teammates and so he will obviously be in the squad that faces Chelsea in the Emirates FA Cup final.
"He is now in the early stages of his recovery and rehab, receiving specialist attention and support from our medical team".
"After the disappointment I accepted the situation and I am now focused to recover to be back on the pitch".