There's no player on the White Sox who is so universally viewed as expendable as Mark Kotsay. He entered the day with a season line of .215/.298/.338 almost exclusively from the DH and 1B positions. He is one of the worst near-everyday players in all of baseball.
And yet there was Kotsay almost singlehandedly powering the Sox to victory. It's games like this that cause a rift between the common fan an sabermetrics.
What do you mean Kotsay is worth negative wins? Remember that game in Detroit that he won almost all by himself?
Thankfully, Win Probability Added (WPA) picks up those wild swings that other metrics might classify as noise. So while Kotsay is listed as a full win below replacement, his WPA total clocks in at a more average but still useless from the DH spot -.08 (not quite sure if that includes today's game)
In the same vein, Bobby Jenks, who once again blew what should have been an easy save opportunity, is similarly as valuable with a WPA -.12 (again today's disaster may not be included). No matter what, a negative WPA from your closer is simply unacceptable. Since more high leverage work occurs at the end of the game, and an average closer converts on 85% of his save opportunities, there is more of an opportunity to wrack up big WPA numbers from the closers spot. Indeed, Jenks managed a WPA near 3.5, where half a point is considered a full win, in 2008 while only accumulating 1.3 WAR. A negative WPA simply shows what all Sox fans are feeling, Jenks is doing more harm than good at the end of games and his time as the closer should be up.