And what is to make us think they can't keep up a solid 3.50-4.00 ERA mark the rest of the way?
Well, that would mean the team would have to be at least 11% better than league average (remember, offense tends to pick up in the second half as rotations tire and so on, so I used 2009's AL ERA), with the upper mark of your hopeful team pitching ERA being attained only with the team pitching 27% above the league average.
So with a team that just lost Jake Peavy and is left with half of their proven MLB starting pitcher commodities being finesse pitchers, no, I don't think that's possible.