The French youngster has been linked with Real Betis.
Wenger told Arsenal Player: "What Coquelin is doing is quite good. His qualities help the team to defend better. He has that ability to fly into people and win the ball back, and that's something important.
"I believe that there's an important stage once a player reaches 19 years of age and is not a regular player at Arsenal. [You must] get him somewhere to gain experience.
"It has two advantages. It lifts the potential of the player, gives him experience at the top level and convinces him that he has a chance to be successful.
"When the player comes back, he has experience and knowledge and you don't have to suffer for the mistakes of a beginner. It gives you more comfort to play him. I never felt that it was finished for him here. I always thought that that's a learning process of the top level."