"Gallas is key for me," declared Wenger. "He has taken his role as captain very seriously and is leading the team well on and off the field.
"I believe he has become very competitive compared to last year when he was injured a lot."
Wenger added: "I had no idea when he signed he could be captain, I had to discover him slowly.
"At the start it was not obvious for him. He had to adapt to a new club, but slowly he has done very well."