Darren Campbell has warned former sprint team-mate Dwain Chambers that he will find it difficult to adapt to the physical nature of rugby league as he begins a trial with Castleford.

Campbell had a run-in with Chambers last year in the wake of his return from a two-year drugs ban.

"He's making certain decisions that I don't really understand because it's going to be difficult to go into a sport like rugby league," he said.

"I would almost say he would have been probably better to go into rugby union, because you probably get hold of the ball a lot less.

"In union, I think there's a little bit of padding on the shoulders - whereas in league it's every man for himself.

"It is a brutal game, a very quick game. Endurance is obviously another part of the game, as well as the speed and the strength.

"Dwain is in a situation where he's trying to earn money."

Great Britain great Alex Murphy vehemently criticised Castleford's move for the athlete while another former international Garry Schofield labelled it "an embarrassment to our game" and called on the RFL to prevent him from competing.

But Chambers will be registered with the RFL, and his arrival at Castleford was welcomed by two of his new team-mates.

Former New Zealand international Awen Guttenbeil, the club's co-captain, said: "The players are extremely excited to have an athlete of Dwain's calibre come into the squad. I am sure there is a lot we can learn from him.

"From a club perspective, we hold a zero tolerance towards drugs - whether they are performance-enhancing or recreational - but Dwain has served his time, and the rules of our game state that you can partake.

"We are about results and we haven't been getting too many results of late.

"It's going to be a big 'ask' for Dwain to be involved and learn the game, but I am sure he can contribute as a world-class athlete."

Sporting Life / Eurosport