Whether the Royals are paying Ervin Santana too much, or should have acquired him in the first place from the Angels, is of little consequence to the fantasy owner. What matters with that fantasy context in mind is whether or not Santana, who has been a quality pitcher in the past, is someone that can be relied upon to produce going forward. If you remember what he looked like in 2011, the answer is an obvious "yes." Unless, of course, you also saw him pitch in 2012. That's where things start to get a little muddied.
Santana's only consistency is found within his inconsistency. In some ways, he's a lot like Alex Rios in the way he's treated fantasy owners alternatingly as friends to be helped or enemies to destroy. Santana, though, doesn't have the kind of ceiling Rios does, and therefore, it's usually easier to wait on him at draft time, or pay less at auction to acquire him.
The source of this inconsistency? Santana's slider. He can be likened to another pitcher with the same issue, Francisco Liriano. When Liriano is on, he's excellent. When he's not, it's generally because his slider is off-kilter, and he doesn't have the other pitches to compensate for that problem. His slider (and Santana's) is so, so good, that when it is on, it's enough. That balancing act is tough to keep up all of the time, though, hence the hair-pulling frustrations owning either of these pitchers has caused you in the past.
In 2011, Santana's slider was worth 24 runs according to PITCH f/x pitch values. It was the only pitch he threw that netted positive runs. He ended up throwing nearly 230 innings, with a 3.38 ERA. His slider was just that good. Enter 2012, where his slider was nowhere near as valuable (10 runs). The result? His fastball was destroyed even more than usual, his change-up couldn't make up the difference, and his ERA shot up to 5.16, courtesy two homers per nine, and despite a .241 batting average on balls in play.
Kansas City would help him as a new locale, were he not leaving a park that helps pitchers out. The home run park effects for KC are very pitcher-friendly, but not as much as those of the Angels. In fact, Kauffman is much closer to neutral than life in faux Los Angeles was, meaning Santana's new environment might be working against him in a relative sense.
The park doesn't matter nearly as much as the condition of his slider, though. He was better in the second half, but not enough, and his ERA continued on the same roller coaster path it had been on all season long. His 4.34 ERA in the second half was helped out by a .218 BABIP -- even if his homer rates come down from where they were, the regression of his BABIP back towards his career rates is going to kill his value.
What does this all mean from a fantasy standpoint? He's leaving a stronger team for a weaker one, so, leaving aside even how he does, there will be fewer opportunities for wins. He's moving to a park where he might get less help from his environment than he did previously. He has two modes here: one where his slider works and he's valuable, and one where it doesn't, and he's terrible.
There's a lot of uncertainty there that can't be figured out over the course of the winter: it will take seeing how he's throwing the ball again to know which Santana has showed up. But, since he's coming off of a terrible year, his price is sure to be low heading into 2013 drafts. Keep that in mind, and draft Santana in order to stash him only, not to use him. Don't set yourself up to rely on a bounceback, essentially, but enjoy that return to form if it does occur.