Although Schilling may be one of the biggest, loudest, most irritating blowhards ESPN has ever hired (and that's setting my anti-Boston bias aside), he did pitch in both leagues and in two of the hardest divisions in baseball. Couple that with Vazquez's checkered statistical history and in this case Schilling is hard to refute.
In any case, Javier may not develop into the outstanding pitcher that he has shown flashes of in the NL. But the Yankees didn't sign him to be their ace. They have enough money invested in CC Sabathia and A.J. Burnett for that purpose. Javier simply needs to keep the team in ball games, allowing the offense to take care of the rest. If he can do that, he will, at the very least, notch some wins for his club.
To this point, Schilling once again shockingly bases his commentary in reality (apparently setting his own bias aside); "On that team with that offense, he can win a lot of games. You are not asking him to lead your rotation."
Even if Vazquez does struggle Schilling is correct. He likely will win roughly 15 games based near-totally on offensive production. And if that turns out to be all the Yankees get out of Javy as their No. 4 starter, they will be in better shape than most teams in baseball including their division rival Red Sox.