Run differential shows that they are grossly underachieving. Doesn't mean they should have the same record as their run difference indicates.
When you use inferior talent in place of superior talent, that will cost you games. He's done that all season, especially with the bullpen. That's not debatable. His 2nd best reliever this season is now a mop up guy. One of his other good relievers is barely used (Lowe). All while Schultz, Tepera, Castro, Loup, etc, have gotten turns as high leverage relievers at points in the season. I mean, come on.