Funny, you always seem happy to dismiss stats as nonsense in certain situations yet use them to put forward your argument in others...
Anyway, it's hardly fair. Valencia's played in his best position all season, and has basically started every game (up until we signed Mata at least). Kagawa has been forced out wide and what-not, has had injuries and goes multiple games in a row without starting.
I'm not trying to justify Kagawa's form, I'd expect better from a player as good as him, but he's clearly not been afforded the same luxuries Valencia has and it's also clear that Valencia has become a pretty shit footballer where as Kagawa is still a very good one who isn't fitting in here due to many reasons.