FORT MYERS, Fla. -- When Twins All-Star closer Joe Nathan went to Minnesota on Monday to have an MRI and CT scan on his sore right elbow, he and the Twins were expecting encouraging news.

The prevailing thought was that the procedure was merely precautionary, that the tightness and soreness that forced him out of Saturday's game against the Red Sox after retiring just one batter was simply a result of the breaking up of scar tissue following his October surgery to remove bone spurs and loose bodies in the elbow.

On Tuesday morning, however, the news Nathan delivered was not good. He was diagnosed with what was termed a "significant tear" to the ulnar collateral ligament in his right elbow. To repair it would require Tommy John surgery and he would miss the 2010 season, but Nathan will not immediately opt for that. Instead, he will rest and rehab, working to build up the elbow over the next week or two. After that time period, Nathan will make a determination if he can pitch with the injury or will need an operation to repair the tear.

"Right now, I want to take it one step at a time," said Nathan, who appeared to be working hard to contain his emotions. "I'm going to work as hard as I can in that week or two to be as strong as I can and hope the arm responds, that it feels good enough to go out there and throw. I don't want to look past that right now. My thought is I'll be fine in a week or two and I'll be ready to go.

"Obviously, this wasn't the news I wanted to hear. It definitely came as a bit of a surprise. At the same time, I have to be patient right now. We'll see how it feels in a week or two."

Nathan believes the injury occurred when he was on the mound on Saturday, an outing in which he struck out one and walked two before exiting. Whether or not he can build up his elbow enough to pitch effectively with the tear remains to be seen, but Nathan is committed to doing his best to make that happen.

"We're going to pursue some other avenues here," Twins general manager Bill Smith said. "We're going to let things quiet down for a week or two and see if we can get some of the soreness out. Trainers are going to work diligently on it to build up strength in that elbow, then we'll re-evalaute."

The results from Monday's tests are being sent to elbow specialist Dr. James Andrews, who performed the procedure in October. There isn't a strong history of pitchers being able to perform with a torn UCL. Takashi Saito had a 50-percent tear two years ago and didn't have surgery. Though he missed a chunk of the 2008 season, he saved 18 games that season and had a 2.43 ERA in 2009.

"Everybody's different, every case is different," Nathan said. "I could be one of those guys, I might not be. I'm going to do whatever I can now to give myself the best chance to go out there and get on the mound and help this team win. At the same time, I'm not going to let this go on too long. I know these guys have a decision to make. They have to prepare for a season, too. I will make a decision quicker, rather than later, and give them ample time to prepare."

Gardenhire said he and his staff will begin doing just that as Nathan attempts to rehab the elbow. It won't be easy to replace the guy who set a team record with 47 saves in 2009 and has collected the most saves in baseball, 271, since 2004.

The Twins could turn to some in-house options if Nathan is unable to return. Jon Rauch has the most closing experience, with 26 career saves, 18 of which came in 2008. Matt Guerrier has developed as the team's top setup man and it's possible the Twins could give him a crack at closing out games instead. Jesse Crain was once thought of as a future closer candidate, and before missing all of 2009, Pat Neshek was thought of as a guy who could finish games if needed.

If the Twins want to look outside the organization, they could try to orchestrate a trade. The one who seems most readily available is the Indians' Kerry Wood, who is under contract for $10.5 million for 2010 with a vesting option in 2011 if he finishes 55 games.

"Obviously, we're going to have to start thinking about that," said Gardenhire, who made it clear it would be Nathan's decision whether he can pitch or not following this rehab period.

"Right now, until they tell me Joe's not going to pitch, he's our closer. But we have to start looking in other directions and start the thought process. This all of a sudden came up. It is what it is. No one's going to cry for us. We just have to try and make our way through it. Right now, our focus is on Joe and where we're at with Joe. We'll sit down as a staff and with Billy and start looking at our options as we go along."

Nathan had been looking forward to helping the Twins win in 2010, and he was excited by the personnel moves made during the offseason and moving into the team's new ballpark, Target Field.

"That's probably the hardest part of this," Nathan said. "Yesterday, flying home, that's probably the one thing that was on my mind the most, was how excited I am for this club, the new stadium, a lot of factors. It's tough.

"I know if I can, I will. If I'm able to go out there and throw, then I'll give it a shot. The only reason I would get the surgery done is if I was unable to go out there. If it's like it was on Saturday, then there's just no chance."

I might pick the White Sox to win the division now. Honestly I was looking for an excuse to do it, I'm not crazy about the Twins because I think their starting pitching is really blah, but I think they easily have the best offense in the division, and they had a great bullpen. It'd still solid but losing Nathan is a huge blow. I just hate the White Sox' offense, but I think they have the best 1-5 in the division with a solid bullpen.

Yeah, but their #2 is Carl Pavano. Or #3 if you toss Slowey ahead of him, who I'm also not expecting much from. I like Baker but that's it.

Nathan out for the season with elbow surgery. Ouch.