Phelps' image has been anything but static. First seen as a prodigy — he was being flown around Europe before the 2004 Athens Olympics by Visa — he was arrested for driving under the influence after returning with six gold medals. After Beijing, Sports Illustrated named him its Sportsman of the Year in 2008 and featured an article that focused on his interaction with children. Months later, a picture surfaced of him smoking from a bong.
He learned a valuable lesson from that incident, which cost him a sponsorship deal with Kellogg. Subway, Visa and other sponsors stuck with him, though, in part because of the way he handled the situation.
Phelps' pride in Baltimore's reputation as a hardworking blue-collar city made him a natural to endorse Under Armour, the apparel company that grew out of a basement workshop into one of the city's most lucrative businesses.
"People have to understand, to have that much success and popularity at such a young age, that's not easy to deal with," said Matt Mirchin, Under Armour's senior vice president for marketing. "He's done better than most, and the maturation we've seen, that's a natural part of it."
Continuing to evolve and shed the near-robotic efficiency and remove, forged through tedious repetition that dominated the last 16 years of Phelps' life, will be the key to capitalizing on one of the greatest athletic careers of all time, Morgenstein said.
"Michael is in rare company, and his name will always resonate," he said. "But eventually, the people move on. There's always somebody next. For him, it's going to be about how well he learns to tell his story, how he takes it and makes it relevant and lasting."
Phelps won't wait long to begin the transformation. His schedule is booked for the next three months and includes both down time and business appointments, Carlisle said. He's planning a world tour that will involve promotions for many of his major sponsors (a list likely to grow but currently including Speedo, Visa, Omega, Head & Shoulders, Subway, Under Armour, Hilton, HP, Master Spas, 505 Games, PureSport and Topps).
Phelps will headline Under Armour's continued push into China with several appearances there. The company recently opened its third store in the country where Phelps won eight gold medals. He'll once again be a part of Subway's marketing push in Baltimore, wearing Ravens colors.
"He's got to be who he is," said Tony Pace, Subway's chief marketing officer. "I don't think it's about creating a new persona. We want him to be authentic."
Finding out who you are after a youth spent as an elite athlete isn't easy.
Dominique Dawes, the Baltimore-area native who starred on the gold medal-winning 1996 U.S. gymnastics team called the Magnificent Seven, found it difficult transitioning into her life's second act.
"I was acting, I was speaking, I was looking into other things," Dawes said from London, where she is working as an analyst for Fox. "But it's very rare to find something that you can be really passionate about. You can like something, but if you're not good at it — and you've been used to being at the level elite athletes are at — that can be too hard."
After an absence from elite competition, she qualified for the 2000 team that finished fourth but received the bronze medal after China was disqualified for using an underage competitor.
After her second Games, she thought she was ready to build a new identity.
"As much as I was ready to leave," Dawes said, "I didn't want that chapter in my life to close. There's no real way to replace it. I went through some dark days — a lot of them — as I figured out what was next."
Now she's a sought-after motivational speaker, and makes appearances on behalf of sponsors such as Hormel. She's also the co-chair, with New Orleans Saints quarterback Drew Brees, of President Barack Obama's Council on Fitness.
She has met Phelps and believes he'll fare well. He'll continue to have opportunities, she said, not only because of his accomplishments but because of his unusual size and shape — "People will always recognize him."
An athlete's ego and self-esteem shouldn't depend on the sport, Dawes said. "But it is. And it can take a while to really be able to move on from that."