For the full story on C.J. Nitkowski's risky medical procedure and baseball comeback, watch CNN Presents, Sunday night at 8ET.
Alpharetta, Georgia (CNN) -- At 39 years old, Christopher John Nitkowski really has no business trying to pitch in the major leagues. In the harsh reality of professional sports, he's a has-been.
Just don't tell him that.
The former first-round draft pick last pitched for the Washington Nationals in 2005 after a 10-season career spent mostly as a left-handed reliever.
"You go as long as you can," he told CNN. "I had a good friend tell me, 'Man, just make them tear the uniform off of you. You can do whatever you're gonna do for the rest of your life. You can't play baseball forever.'"
In the middle of the 2011 baseball season Nitkowski announced in a first-person article for Sports Illustrated that he would try a comeback. After his brief major league appearance in 2005, he pitched subsequent years for one team in Japan and three in South Korea.
This time, he wrote, he would agree to a risky medical experiment that would involve injecting his own stem cells into his injured pitching shoulder, which he hurt in an initial comeback attempt last spring.
Nitkowski was following the path of 37-year-old Bartolo Colon, who in late 2010 went through the same procedure. Colon wound up restored to health and pitched credibly for the New York Yankees in 2011.
Nitkowski telephoned the doctor who treated Colon and agreed to pay about $3,000 for the procedure.
Nitkowski and the physician, Dr. Joseph Purita, agreed to CNN's request to follow the procedure and report on the outcome, no matter what that turned out to be.
In late August, Nitkowski went to Purita's Florida office and watched as some of his own stem cells were extracted from fatty tissue around his waist. The stem cells were then spun in a centrifuge and emerged as something called platelet rich plasma (PRP), which athletes have been using in recent years to restore their health.
Nitkowski returned several weeks later for a follow-up PRP injection. No human growth hormones, which are a banned substance in major league baseball, were used.
Both Nitkowski and Purita told CNN they were well aware of the risks.
"We really don't have a good uniform idea of what constitutes platelet rich plasma," Purita told CNN. "I mean, what is it? You could ask 10 doctors and they're going to give you 10 different answers. We really need to get together and form an idea as to what it is."
One doctor contacted by CNN says the whole process is essentially worthless.
"There are many, many misstatements, direct inaccuracies and errors in the way that growth factors and stem cells are portrayed," Dr. George Daley, president of the International Society for Stem Cell Research, said after reading an informational packet written by Purita, available to patients on his website. "If it were subjected to a critical analysis by experts in the field, it would be dismissed as unfortunately superficial and inaccurate."
None of that seemed to matter to Nitkowski, who said all he wanted was a chance to pitch one last season in the major leagues. CNN followed him after his injections through a grueling series of workouts. First, he had to regain his arm strength by hitting tennis balls hurled at him by a machine. Then, he had to throw a football at a moderate pace. Finally, in October, he began to throw a baseball again.
Nitkowski felt that his arm strength was back to normal and his fastball was back to its usual velocity. Nitkowski has converted himself into a sidearm pitcher, abandoning the customary over-the-top delivery. His specialty, he said, would be to come in briefly in the late innings of a game to get one or two left-handed batters out and the unusual pitching motion would make him more effective against lefties.
But finding a spot on a major league roster would be difficult, even if he were healthy and even though left-handed relief pitchers are a valuable commodity.
CNN Correspondent Drew Griffin talked to Nitkowski at his home in suburban Atlanta.
"Do you ever lay in bed and think, 'Am I delusional?'" Griffin asked.
"There's times where you question yourself," Nitkowski said. "Anything you want to do, if you have a passion about it, you're gonna do whatever it takes to do it. And so that's where I'm at. There's times doubt definitely creeps in."
On New Year's Day, Nitkowski found himself at a baseball stadium in Santo Domingo, capital of the Dominican Republic. He had paid his own way there to try out for a job as a reliever for one of the four teams playing in the Dominican Winter League round-robin playoffs. His agent had a friend who was also an agent in the Dominican Republic.
After two days of waiting, Nitkowski finally had his tryout -- and he won a job. The pay for two weeks with the Dominican League Gigantes? $2,500, less that one-fifth of what a major-league rookie makes.
Nitkowski pitched in five games during the Dominican postseason. He didn't allow a hit in his first four appearances but gave up four runs in final game there.
When he returned to the United States, he couldn't find any big league teams interested. He changed agents. Finally, he managed to get a tryout with the New York Mets. Again, he thought he did well but there was no contract. No return to major league baseball.
C.J. Nitkowski is still at home without a pitching job. He's helping coach several youth teams. He still works out and contemplates pitching in an independent league.
He was able to get a temporary baseball-related job. He auditioned for a role in an upcoming movie biography of Brooklyn Dodgers general manager Branch Rickey, who signed Jackie Robinson to his first major league contract. Harrison Ford will play Branch Rickey. Nitkowski will have a speaking role as a pitcher on one of the Dodgers' opponents.
He just hopes that it won't be his final time on the mound.