Santana was pretty good or at least decent through his first 4 starts as well (2.60 era in that stretch).
As far as Pelf's overall numbers, I don't really think the weight of Pelfrey's April and May starts have any relevance anymore with 3 months of more recent and more terrible results (5.76 ERA for Pelfrey over the last three calendar months, when the wheels fell off).
I'm also swayed by the fact that Santana actually has a track record of being a decent pitcher, way above anything Pelfrey has. Evidence suggests Neil Allen did identify some mechanical issue after putting him through SS drills prior to the first of his 2 sparkling starts against Houston. Maybe it will be a fluke, we'll see.
But most importantly, with as shaky as the bullpen is, we don't need a guy that has failed to finish 5 innings in 4 of his last 6 starts, not even getting out of the fourth 3 times. That's what makes me most queasy with Pelfrey.
Then again, I'm not sure how round and round we want to go on this, as it's not like Hughes was exactly lighting it up either.