Dwain Chambers today revealed he was "optimistic" that he would be able to compete in the Olympics this summer.
Chambers has begun a one-month trial with Super League strugglers Castleford Tigers but admitted a legal challenge to his Olympic ban for failing a drugs test is "likely."
The 29-year-old has served a two-year drugs ban but is banned from running in Beijing because of a British Olympic Association by-law.
Speaking about an appeal, Chambers said: "We remain optimistic, we can't afford negative thoughts.
"There will be a decision on that in the next couple of weeks if we want to go forward with a legal case."
Chambers' solicitor, Nick Collins, added on Sky Sports News: "It's always been a very realistic aim we will be going there (Beijing).
"There's been some very encouraging comments from people outside the BOA saying they have no problem with Dwain.
"We wouldn't take it (an appeal) on if we didn't think there would be a reasonable chance of success.
Chambers insisted the Olympics remains his priority but felt he had to explore other options should his appeal fail.
"I would like to get to Beijing - I'm getting on and am 30 on Saturday and this may be my last chance," added the sprinter, who said he would be taking advice from rugby league legend Martin Offiah.
"But I am here to learn and see if I can grasp a different sport.
"I'm going to take it one day at a time and instead of running in a straight line I will be running left and right.
"I'm optimistic about what I can achieve. I'm competitive at heart and want to go out and do the best I can."
Castleford coach Terry Matterson admitted it would be difficult for Chambers but said the athlete and the club were right to take the gamble.
"It is going to be a tough ask, no doubt about that but nothing ventured, nothing gained."
Football manager Michael Robinson said Chambers would not be paid for the month he was on trial, which he insisted the club was taking seriously.
"It was never mentioned as a publicity stunt," he said.
"It was made clear from day one there is no money changing hands between Dwain and the club in the first month."Reuse content