Arsenal are facing a fight to keep another one of their top young players after Amario Cozier-Duberry joined Brighton this weekend. Cozier-Duberry opted not to stay on with the Gunners despite being in and around the first-team last season and instead has gone to Brighton in the hope of playing more. Gunners manager Mikel Arteta is open to allowing players leave if they feel it is best for their development but he won’t want to lose many more. Unfortunately though, it looks like the Gunners boss has another situation unfolding when it comes to another one of his top youngsters. This time, it’s…