He'll visit Dr. James Andrews for an arthroscopic procedure Thursday in Birmingham, Ala., though there's a good chance Mathieson will need another ulnar collateral ligament reconstruction.
Mathieson said he was told by Andrews that a scope might solve the issue, which would keep him out for a shorter time frame. He's not ready to concede his season, yet.
"I'll wake up [Thursday] and I'll either be out four to six weeks or a year," Mathieson said by phone.
Mathieson fell into the 10 percent of pitchers who don't recover from Tommy John surgery. The recovery rate is "about 30" percent for second-time surgeries, though Eric Gagne and Doug Brocail are two success stories.
"He can't pitch the way he is now," Sheridan said. "It's one of those things that has to be done."
"Any significant surgery is hard to overcome, but when you have it again, it's tough" said Cole Hamels, one of Mathieson's best friends. "I wish the best for him. I hope something goes real well for him, finally. He's going to have to keep fighting."
Mathieson received well-wishing text messages from Hamels and Chad Durbin.
If he needs surgery, rehabilitation on a second surgery will be more conservative, Sheridan said. Mathieson won't begin tossing until five or six months after the surgery, instead of the aggressive four.
Hamels predicts that Mathieson won't give up his dream without a fight.
"He achieved every kid's dream to be in a Major League uniform [in 2006]," Hamels said. "When you taste it, you want more. He has to give it everything he has, so in the end, he doesn't regret [not trying]."
At this point, Mathieson maintained his sense of humor.
"I just hope for the best," he said. "I might be the only guy to have surgery performed by the two best doctors in the country. I'm still young, and I hope to come back and pitch. That's my goal, and that's what I'm going to keep working toward."