Yes it could be that simple, I’ve seen some of their fans on Twitter saying he’s been awful all season.Might be as innocent as ehmer has had a poor season on the pitch. Remember the game down there where he fell over to let Oliver score.
Ehmer always seemed very relaxed on the pitch to me, some could mistake that for not showing enough aggression. I get the Impression that Barton likes an aggressive player - that's not really Ehmer.