I've already questioned you on those assists stats so I'll not ask again
Transfermarkt says that Kagawa has 4 asssist in the PL. The reason I mentioned Mata's setpieces, is because I expected people to bring up the goals scored stat. And they did.
Goalless? No. As many as Mata? Definitely not. Kagawa has scored in four games for Utd in 2 seasons. Mata has already matched that.
You have to keep in mind that ever since Kagawa came here, he's struggled with 3 things that Mata hasn't:
1) a very lengthy injury spell
2) playing out of position for the vast majority of the time
3) spending a lot of time on the bench
In fact, Kagawa has never been given the same run of games as Mata has for us. What's even worse, is that Mata already has had more minutes in the no.10 role than Kagawa has. Or they're around the same number of minutes.
But even if you completely ignore these more than reasonable variables, you have to realize that Mata's greatest strength, is his effectivity. He's like a striker in the way he takes his chances for assists and goals. His overall play besides this, is not better than Silva, Özil and even Kagawa. What makes Mata unique, is his setpieces and effectivity. That's why I actually
expect him to have
significantly more goals/assists than Kagawa. But he really hasn't, if you take the variables above into consideration.
You're last point is incorrect and irrelevant anyway. Dortmund are not better than every team in the Premier League. If it was true it would only further serve to make Kagawa's job in that league easier anyway which would make him seem like a player only suited to playing weak opposition in a much stronger team.
This is word against word, but I still think that Dortmund is better than City, Liverpool and Chelsea.
Kagawa played 4 games combined against Bayern, and was generally brilliant. He's also played great games for Japan in games where they were the underdog(vs Italy, for instance).