Tests on Nathan's right throwing elbow have revealed a significant tear in the ulnar collateral ligament, an injury that could require season-ending Tommy John surgery. Nathan's 246 saves over six seasons are the most in the majors during that span.
The Twins shared the grim news Tuesday in Fort Myers, Fla., before their exhibition game against the St. Louis Cardinals. General manager Bill Smith said the plan is to first give Nathan time to let soreness and swelling subside -- and build strength in the muscles around the joint -- before a final decision about surgery.
In the meantime, a second opinion will be sought from Dr. James Andrews, the noted surgeon who removed bone spurs and chips from the elbow in October. The ulnar collateral ligament is replaced in the Tommy John procedure, which typically takes 12 to 18 months to recover from.
Nathan will try to pitch again in two weeks. If he can't, the four-time All-Star will have surgery. His season then would almost certainly be over, perhaps putting his status for next year in question, too.
An emotional Nathan said he's prepared to try to pitch through pain.
"If I'm able to go out there and throw, then I'll definitely give it a shot," Nathan told reporters in Fort Myers. "The only reason that I would get a surgery done is if I'm just unable to go out there."
It is possible to pitch through the injury.
"I could be one of those guys. I might not be," Nathan said.
But if his elbow hurts like it did on Saturday, when he first felt discomfort and was removed from an exhibition game against the Boston Red Sox?
"Then there's just no chance," Nathan said.
Nathan and the Twins initially believed this weekend he was just dealing with general stiffness and soreness. He flew to Minnesota to meet with team physician Dr. Dan Buss on Monday.
The surgery decision won't be delayed too long.
"They've got to prepare for the season, too," Nathan said.
The 35-year-old Nathan signed a $47 million contract two years ago that guarantees him $11.25 million this season and next. The Twins have a $12.5 million option for 2012, with a $2 million buyout.
"Obviously this wasn't the news I wanted to hear," Nathan said. "It definitely came as a bit of a surprise, but at the same time I've got to be patient right now and take this a step at a time. We'll see how it feels in a week or two."
Nathan was 2-2 with a 2.10 ERA last year, with a career-high 47 saves. He was vulnerable down the stretch, surrendering four of his seven home runs in the final month of the regular season. He gave up a tying two-run shot to Alex Rodriguez in the ninth inning of a Game 2 loss to the New York Yankees in the first round of the playoffs.
Losing Nathan for any amount of time would be a big blow to the Twins, who shored up their lineup and are eager to celebrate the opening of their new ballpark, Target Field, with another trip to the playoffs.
"That's going to be a huge drop for them," Chicago White Sox infielder Omar Vizquel said at Scottsdale Stadium in Arizona. "It's not going to be easy to replace a guy like him. He pretty much guarantees a save every time."
Right-handers Jon Rauch and Matt Guerrier are probably the top two candidates to replace Nathan, but Rauch is the only Twins reliever with even limited prior experience as a closer. Rob Delaney and Anthony Slama are well-regarded prospects who could be considered.
"Right now, until they tell us 'Joe's not going to pitch,' he's our closer," manager Ron Gardenhire said. "We'll go from there, but we have to start looking in other directions and start the process. This kind of all of a sudden came up, and it is what it is. No one's going to cry for us. We just have to kind of make our way through it."
Guerrier wasn't ready to talk about replacements.
"I'm more concerned about how he's doing," Guerrier said. "He's still pretty emotional."
White Sox manager Ozzie Guillen remembered one comeback by his team against Nathan, last summer.
"Besides that, I don't remember if we even scared the guy. He's so good against us," Guillen said. "I'd rather face anybody out there, no matter what kind of pitcher they are, than face Nathan."
Nathan's injury was the news of the day around Minnesota's AL Central rivals.
"The Twins seem more than any team when people go down, whether it's players or pitchers, to have other guys step right in," White Sox first baseman Paul Konerko said. "It seems they never rest a beat. So they will probably do the same thing with that: It will be some player that no one is even thinking about right now that will probably be lights out for them."