"I still see a lot of things, unfortunately in the sport, that are just horrible," said Nelson, the longtime president of the Track and Field Athletes Association , which supports the rights and interests of pro athletes. "The only way I can influence change is to get back involved in the system as more than just a bureaucrat, as a participant and live the life that athletes live.
"Plus, I want to inspire athletes of all ages. Just because you're not 25 doesn't mean your days of competing or challenging yourself to be stronger, faster and better than you were yesterday are over."
Nelson's return was launched last summer on a dare. He was working with a high school shot putter when the father kept baiting Nelson to throw, something he hadn't really done since missing out on an Olympic spot during the 2012 trials.
"I was like, 'I'm not going to throw. I'm too grown up to be manipulated into it by peer pressure,'" said Nelson, who officially retired in January 2013 and lives in Athens, Georgia. "So about 35 minutes later, I found myself taking my first throw in about three years."
And while it was a lighter shot put, he tossed it pretty far.
"I was like, 'That's kind of interesting,'" he recounted.
All the more since he was searching for some kind of activity to quench that competitive fire.
"Some people have a passion for running. Some people have a passion for swimming," explained Nelson, who also captured a silver medal at the 2000 Sydney Games. "Over 15 years of doing this, I just developed a passion for throwing things."
The three-time Olympian and father of two daughters remained in tip-top shape, even lighter than he was when he last competed. He found training time after running a sports performance training center (and later after serving as director of business development for his agent, Paul Doyle). Nothing too crazy, maybe an hour's worth of throws.
Nelson began the paperwork for a return last summer, just in case the desire to compete at trials struck, which, of course, it did. He also re-entered the drug testing pool.
"I would imagine if I throw much further, I'll be put back on a high-priority (testing) list, because I'm a shot putter and 40 years old," he laughed.
The longtime anti-doping crusader welcomes testing. The more, the better. Anything to weed out the dopers in a sport that keeps taking hits.
Most recently, track's governing body upheld a suspension for the Russian team imposed in November after a World Anti-Doping Agency report detailed widespread, state-sponsored doping. It allowed an exemption for athletes who can show they've been subject to reliable drug-testing outside their home country.
"Last year, when we had all these crazy revelations starting to occur, it lit another fire," Nelson said. "Because doping is a black cloud that hangs over the sport and continues to beat down the potential value athletes may gain out of positive stories."
His first meet back was a small competition in Athens, Georgia, two months ago. His top throw was 67 feet, 2 ¼ inches (20.48 meters). His personal-best is 73-10 1/4 (22.51 meters) in 2002.
For trials, Nelson's goals are modest: Break the age record for a 40-year-old, which is 70-3 (21.41 meters) by Brian Oldfield in 1985.
Hit that mark and Nelson has a chance at securing one of the three spots on the U.S. squad.
"I suppose on some level it's in the back of my mind that I could make another Olympic team," Nelson said. "It would be pretty epic to do that at 40."