British sprinter Dwain Chambers will miss the indoor season and may not race again, says his agent Cubie Seegobin.
Chambers must pay back a percentage of future track earnings
Chambers, who returned to athletics in June after a drugs ban, has to pay back any prize money he won while competing on steroids from future track earnings.
The 28-year-old is hoping to make a career in American football.
"Personally I think because we have so much money to pay back, if he can find another way to make a living he will," Seegobin told BBC Sport.
"He won't be competing indoors, that's for sure.
"Dwain might only have a year or two of competition left and will have to pay most of his prize money back. This is my logic, not anything he's told me.
"He's training in England and will be ready for the outdoor season, but there are other things he's putting his attention into."
Chambers, a former European 100m champion, was given a two-year ban from athletics in February 2004 after testing positive for the banned steroid THG.
Dwain did better than the coaches expected - he was tougher than they thought
Director of public affairs
He made a startling return to the track by recording 10.07 seconds in the British Grand Prix 100m in Gateshead in June.
But it proved something of a false dawn as he finished only seventh in the individual 100m at the European Championships in Gothenburg, although he did win gold in the relay.
The 28-year-old Londoner took part in a training week for NFL Europe in Cologne at the start of November and is waiting to find out if he will be invited to a six-week camp in Florida in March.
The NFL Europe season runs from spring into early summer, making it incompatible with training for the athletics season.
Seegobin, who is based in Los Angeles, said he had spoken to Chambers last week and added: "He's waiting to hear from NFL Europe.
606 DEBATE: Would Chambers be right to quit athletics?
"When he tells me what he needs me to do I'll go and do it".
About 80 people will be invited to the NFL training camp in Florida in March.
Forty-eight of them will then be selected for the draft and eligible for the six NFL Europe teams, Amsterdam, Frankfurt, Berlin, Cologne, Dusseldorf and Hamburg.
David Tossell, director of public affairs for NFL international, said Chambers would find out whether he had been selected for the Florida camp "this side of Christmas or just after".
Tossell said the Londoner had impressed the coaches during the training week in Cologne in November.
"Dwain did better than they had expected - he was tougher than they thought," Tossell told BBC Sport.
"The important thing was to see was how he'd react when hit, and he picked himself up and carried on.
If his heart's not in the sport, then follow your heart
"I had been quite surprised when the phone rang and it was Dwain saying he wanted to come along to the training camp.
"We sat down with him and explained how difficult it would be. There are huge odds against him making it and we made sure he understood that.
"But he is very determined and that's impressed us. And he has a vital quality that you can't coach - raw speed."
Chambers' fellow British sprinter, Mark Lewis-Francis, told BBC Sport: "I heard he's not coming back to the sport, or something like that.
"If his heart's not in the sport, then follow your heart. If his goals and dreams are somewhere else, all I can do is just wish him the greatest of luck.
"For me, Dwain was a great competitor and rival. I enjoyed competing against him."