Ireland does deserve to start IMO. But he has to be fit and I don't think he was for much of last season. But that's not the root problem IMO.
IMO the problem with Mancini and Ireland is really a problem of Mancini and any playmaker. We have 3 forwards who pay with their heads down...Bellamy, Ade and Tevez. They all have great talent so I'm not saying they should go. But they need to look up or at least Mancini needs to figure out how any playmaker (Ireland or anyone else) can work with them.
Ireland can stay or go, Kaka can come or not. Gerrard, Milner, Arteta, whoever. Mancini needs to fix how we play or no player in Ireland's mould will work. Therefore I think the problem is less likely to be resolved by Ireland's head and more by Mancini's tactics/training.