I'm not silly... YOU'RE silly
All I'm saying is that we really don't know if Cowser is going to produce any better than what O'hearn offers. His minor league performance indicates that he deserves a chance. But until he's wearing a big league jersey and gets in the box against big league pitching for an extended period of time, we won't know if he's any better. The OP said he had "to believe Cowser will be a better player for the rest of the season in the majors." Well that's a hope, not a surefire fact.
Believe me, I want Cowser up. But I'm aware that not every prospect translates minor league success into major league success.