See I remember a time before Martinez when Kev was probably our best player for at least a season and a half. People can argue that and if you don't think he was our best player, then he was certainly our most dangerous and exciting.
Then the likes of Barkley, Lukaku and Delofeu came along - all younger and all who made a bigger impact in their own ways. Kev couldn't handle not being as important anymore culminating in his penalty antics at home to West Brom where he stole the ball from Baines. It was almost as if he was trying to say "look at me, I'm still important too".
Sounds like he is still a little bit of that mentality, but we also know there is (or maybe was) a player in there somewhere.
He definitely needs man managing and ego massaging to get the best out of him. He could still be a useful player to have in the squad IF he can be kept happy. If not, then good luck to him - he has provided some memorable moments in the past and I will choose to remember his positive contributions over the years (as despite what others might think, I believe these outweigh anything negative.)
Ooooohh Kevin Mirallas!