Dwain Chambers, the 30-year-old sprinter, will make his rugby league debut tomorrow and, if it leads to a £60,000 annual playing contract with Castleford Tigers or another club, turn his back on his ambition of running in the Olympic Games.

Throughout his month-long unpaid trial at Castleford, Chambers has refused to rule out a legal challenge to the British Olympic Association's decision not to consider him for selection for the Beijing Games in August after he was given a two-year drugs ban in 2003. But speaking before his appearance in a specially arranged reserve-team match against York City Knights, Chambers said of a playing contract: “I would take it. I'd have to. Why would I turn down the opportunity to play rugby and have fun for the next three years, earn a living for my family and live in a nicer place? It would be disappointing not to run in the Olympics, but who's to say this wouldn't be more satisfying?

“At the moment my head is in rugby. It's impossible for me to live in two worlds. Should this door close on Sunday, I'll still be fit and ready to run. Playing rugby league has got me fitter than I could ever believe. I'm not closing the door on the Olympics, but I have to deal with this first.”

There will be representatives from both codes to watch Chambers on the wing. As well as other engage Super League teams, Cardiff Blues and Llanelli Scarlets rugby union clubs have reportedly been following his progress. “Every person in rugby league will want to knock his head off and show what he can expect,” Paul March, the York coach, said.

Chambers's opposite number is likely to be Lee Mapals, 22, a former soldier from Leeds with a reputation for scoring tries and breaking tackles.