The guy played at AEK last year (he joined in the winter transfer period) and was simply horrible. Bad positioning, many mistakes and looked really, really nervous. Just not up to it. However, he showed that he has some talent and he could become a very good player if he gets experience. AEK wanted to sign him mainly due to his performances in training (he looked impressive there, he just sucked in real games) and because they believed in his talent but they just couldn't afford him due to their financial troubles (PAO and Olympiakos were never interested) .
He is a promising player but he needs to really grow up mentally. I doubt he can do a job at Red Star right away but the truth is that AEK was a turbulent club last year, definitely not ideal for someone looking for stability in order to improve.