“The average athlete is not investing the same way you’d see a more sophisticated chief executive invest,” Mr. Lee said. “Deals are brought to them in the locker room. That’s not the typical wealthy client. Our goal is to slow that down.”

That is a lesson for any affluent person, given the example of Bernie Madoff and the hundreds of friends who handed over money to him. More common, though, are investment tips and strategy suggestions floated by people at clubs or work.

Declare Your Next Milestone. Ask retired executives what they worry about, and it’s likely to be some form of staying relevant. Joe McLean, who played professional basketball in Europe and is the managing partner of the wealth advisory firm Intersect Capital, said he counseled his clients to think in terms of milestones.

This accomplishes several things, Mr. McLean said. It allows players to fend off pitches or requests for money. “If you declare a milestone, what it allows you to do is focus on that,” he said. “If you don’t have a milestone, money comes in and you have nothing to save it for.”

It also keeps friends from asking for money or gives a player a way to easily brush off the request. “You can say, ‘This is what I’m trying to accomplish.’”

Longer term, a milestone sets a player’s sights on life beyond his sport. Mr. Thomas said he was always hesitant to define himself solely as a football player. During his playing career, he continued to have hobbies, but he also maintained his interest in real estate, which began in college.

As the end of his professional career approached, he looked to other players who had been successful in retirement. “The guys who had the most issues were the ones who didn’t have something else to do,” he said. “Going fishing every day sounds great, but if you don’t have purpose and direction, you can struggle a bit.”