Twins closer Joe Nathan has a torn ulnar collateral ligament, tweets Joe Christensen of the Minneapolis Star-Tribune. Christensen's colleague La Velle E. Neal III tweets that Nathan will wait a few weeks and try to pitch with it. If that fails, he'll miss the 2010 season with Tommy John surgery.
As you might expect, the Twins "are considering contingency plans at closer," tweets Christensen. It's not easy to replace a 2.00 ERA and 40 saves, which is why the Twins are paying Nathan $11.25MM this year.
The Twins have a deep bullpen; I profiled a few backup closer options a week ago. If they decide to look outside the organization, Jason Frasor, Heath Bell, and Kerry Wood have closing experience and might be available. Ken Rosenthal of FOX Sports assesses the Twins' situation in this column, suggesting "the loss of Nathan transforms the Twins from AL Central favorites into mere contenders."