He could've definitely done better at some points, but i don't think he's entirely to blame for this "failed" season. Actually i think he'd do quite well with a couple more signings to add depth. (something we badly missed this season and cost us ultimately)
And if he goes there aren't really many other options (Mou being the only one i'd take back in a heartbeat), i don't wanna see us ending with Benitez for example. Not too mention that i'm tired of changing coaches every season since Mourinho left.