The 25-year old French midfielder has ben sidelined for the campaign so far after undergoing surgery on an ankle injury in the summer but is available for selection as the Gunners prepare to face German club Borussia Dortmund in the Champions League tomorrow night.
Arsenal boss Arsene Wenger was delighted to have Diaby back in the fold whilst admitting that it was a massive night for the North London club who can qualify for the next phase of the competition with at least a point.
"I am very happy - he has not played a minute this season and he had surgery in June," said Wenger.
"Every player and member of staff is conscious that this is a big night for us. We have the desire to win the game."