We can quibble about where each one slots into a rotation. I kind of think Greinke is a soft #1 and a kickass #2, where Sanchez is more of a #3. But that matters less than their track record. They're basically the same age (Greinke is four months older) but Greinke has thrown four 200+ inning years and Sanchez has zero.

I think teams (usually to their detriment, but whatever) would ideally like to shop for high-end free agent pitchers like Edward Norton in "Fight Club" shopping for a sofa. You get one that you can slot into a known and stable front of the rotation spot and say to yourself "that problem is solved". In short, Greinke lets teams do that in a way which Sanchez doesn't.