In theory, yes, but some guys just seem to be able to hit well enough, despite this issue.
I remember posters bashing Papi for his inability to lay off the sinkers down and away. When he slumped, some wanted him moved down in the order or worse.
One thing I've always doubted is that if you mess with a successful batter, who has little strike zone discipline, maybe you mess him up.
Of course, it makes sense that if Rafaela changed nothing else, except to lay off bad pitches, he'd have to be better, but I have to think you are changing a batters whole approach, and you have to be careful what you wish for.