Javy's problems lie in the AL, not in Girardi. To not even be able to go 5 innings is pretty pathetic considering this guy was a Cy Young candidate last year.
His environment is definitely tougher than last year, but that's not all that's causing his problems.
Vasquez has lost about a little over 2 MPH on his fastball from last year (91.1 average to 88.8 average). Predictably, hitters are getting much more contact against him when swinging (80.3% this year, 73.3% last year).
Might be age, might be some sort of injury, but either way Vasquez has not been himself and you can't just blame Girardi/Thames/The AL.