Before we discuss the hidden keeper value in readily available pitchers, it's worth noting that, in general, those players who make their baseball living hitting baseballs tend to be far more safer and reliable than those who do so throwing them. That doesn't mean one should keep Joey Terdoslavich over Yu Darvish, but there are, admittedly, some benefits to keeping hitters. Regardless though, pitchers do account for half the fantasy stats. They are valuable to us.
So after discussing hitters with varying degrees of future value for some keeper leagues, let's focus on the pitchers. Again, I can't possibly know if your league keeps only three players, in which case I'd focus entirely on hitters, or 12, in which case you cannot do this. I participate in a 16-team league in which most closers are kept, and the way I became the owner of Craig Kimbrel was by adding him the September he first burst onto the scene. By the following spring, he was a dominant closer. Starting pitchers can follow this path as well.