Just a few quick thoughts on Jon Lester:
Absent context, the only correct answer as to whether the Pirates should trade for Lester is, "It depends." Some of the ideas that have floated around (Josh Bell and Tyler Glasnow; Josh Bell, Nick Kingham and JaCoby Jones) are way too much for the Pirates to give up.
That said, I'm coming around to the idea that a somewhat lesser package (just Bell and Jones, say) would be fine. I've seen estimates of Bell's value as being anywhere from $18 million to $30 million. In the abstract, there's no way a dozen starts from Lester are worth $18 million, let alone $30 million, and so Bell plus a lesser prospect would be an overpay. But of course we can't look at this purely from a WAR perspective -- the Pirates are in a close playoff race, so wins these next couple months are worth more than a random midseason win would be. And then there's the value of Lester's playoff starts to consider.
Taking a stand here is gut-wrenching, because we don't know how these next few months will turn out, or how Josh Bell will turn out. Maybe Lester will pitch brilliantly and lead the Pirates to a World Series, and Bell will be a bust. Maybe Bell will emerge as a top offensive player and the Pirates will miss the playoffs even with Lester. None of us know, and not knowing is scary.
But if the Pirates make a difficult, but not insane, decision to trade a top prospect for a clear star who dramatically increases their playoff chances and gives them a better shot once they get there, well, we should be able to live with that, even if it turns out badly. The Pirates have an opportunity here, and there is, obviously, a lot to be said for going for it. The trick is figuring out how much is too much to give up.