Dan Haren trade fall-out shows just how fickle pitching careers can be

In an afternoon, Dan Haren went from one of the bargains of the offseason--off to the Chicago Cubs in exchange for a temperamental closer on a one-year deal the Los Angeles Angels appeared to be willing to pay into--to a player who wasn't worth that temperamental closer or those dollars and is now, the trade and the deal having fallen through, a high-risk free agent. We know what he did in 2012; we know he disappointed, generally, and in particular lost velocity and found himself the victim of more homers than usual.

Haren has taught the Cardinals lessons about the fickleness of pitching careers already, of course; sending him to Oakland for a picture of the Mark Mulder from 2002 cost them, according to FanGraphs, 38.9 wins above a replacement-level pitcher.

Now he's back for more, just as the Cardinals prepare to turn their future over to a series of top pitching prospects and debate whether to extend Adam Wainwright's contract, which runs out after the 2013 season. Haren's been one of the most dependable pitchers in baseball since they traded him, and he's coming off a season that makes him a slam-dunk bounceback candidate. And now Theo Epstein's running away from him.

Pitchers are frightening.