I think that you are absolving the player for his own failings. End of the day, the players, not the manager step onto the pitch. Nasri is expecting to be paid as a 'go to' top player - while having demonstrated that he is nothing of the sort. Did RVP's efforts drop in the last 3 months of the season? Wilshere's? Sangna's? If a player is to be paid what Nasri is demanding, then he should not be looking to the manager for motivation. If he is, then he is not ready to be paid that much.
I won't comment on the contract scenario last Summer, but I find it impossible to believe that an overture was not made by the club when so many other contracts were extended. As we are seeing now, you cannot get anything sorted without the willingness of the other party to coopertate. And there would have been no reason back then for club or player to make and failed negotiations public.
One thing people might not know is that he had just signed an extended contract with Marseille when he came to Arsenal. This would suggest that he might well be looking to re-negotiate/leave now even if we had extended last Summer - given that this would have been before his so-called 'breakthrough' season.
Like I say, I am not expecting loyalty. But I see in Nasri a player who, though talented, may well be too self centred to truly realise his potential.