Nathan told WFTC-TV, Minneapolis-St. Paul, that he tried to throw Sunday morning in Florida, two weeks after being diagnosed with a torn ulnar collateral ligament, in hopes that he could continue the season without surgery.
But Nathan, 35, indicated the session did not go well and that he has opted for season-ending "Tommy John" elbow surgery.
"We knew it was a long shot, but what this did do is clear my head," Nathan told the (Minneapolis) Star Tribune. "Definitely was no gray area. Definitely was on the black side, where it didn't go as well as we like, and we know now we're going to have to go in and get some surgery done, get this thing fixed up."
Doctors say the recovery time from the procedure is usually 12 months. Under that scenario, Nathan, who last year saved a Twins-record 47 games, could be ready for the start of the 2011 season.