BP: The cost of Joe Nathan's injury

March, 9, 2010
3/09/10
3:38
PM ET
Attention Twin Cities drugstores: Stock up on antacid. In the biggest news of spring training so far, Minnesota Twins closer Joe Nathan has been diagnosed as having a torn ulnar collateral ligament in his right elbow. Since he will likely miss the entire season, it's time to analyze how this will affect the Twins.

Before today, the American League Central looked like a two-horse race between the Twins and the Detroit Tigers. With Nathan out, it's hard to see the Twins contending. Nathan, who turned 35 in November, was once again slated to be the steady hand at the back of the Twins' bullpen. He's saved at least 36 games in each of the past six years, and has been as good as just about any other closer in baseball during that time.

So, how bad is the loss of Nathan? Well, there are two related, but separate, costs that Twins fans need to worry about. Manager Ron Gardenhire now has to figure out Nathan's replacement on the roster. He'll be a guy who, unless the Twins make a trade, otherwise would have started the year in Triple-A or on the waiver wire. Over the past few years, Nathan has consistently posted WARP3 scores around 6.0 (meaning he was six wins better than the average guy in Triple-A or on the waiver wire), and there's no reason to believe that this year would have been any different. Those six wins last year would have completely rewritten the story of the AL Central, from a neck-and-neck race to the end to the Tigers clinching in the last week and resting up before meeting the Yankees in the ALDS. Nathan makes that much of a difference.

But then there's the other cost of Nathan's injury. Twins fans are probably not thinking about Nathan's direct replacement on the roster, but rather who will take over as closer in his absence. The likely candidates are Jon Rauch and Matt Guerrier, both of whom have their positives, but neither of whom is Joe Nathan. Over the past two seasons, Rauch and Guerrirer have each had a WARP3 hovering around 1.0. Fairly or unfairly, everything that happens in the ninth inning is magnified. Twins fans are used to having an elite closer to shut things down, and they now get to deal with the tummy ache that comes from knowing that a lesser pitcher is handling the last frame. There will no doubt be a few games where the new closer blows a lead and local sports radio lines will fill up with cries of, "Nathan would have saved that!" One thing to keep in mind, however, is that the average closer still converts roughly 85 percent of save chances, while Nathan has converted 90.8 percent of save opportunities for his career. If Guerrier and Rauch can convert saves at a league-average rate, Nathan's injury will be downgraded from a massive catastrophe to a medium-sized catastrophe.

Russell Carleton is an author of Baseball Prospectus.

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