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7th January 2019, 18:19 | Castleford
The 28-year old was left without a club when he was not offered a new contract with Hull KR at the end of 2018 and now has a chance to earn a deal with the Tigers.
Clarkson, who made his Betfred Super League debut for the Rhinos in 2010 and was a member of their 2011 Grand Final-winning team, will spend the rest of pre-season with Castleford.
"I was over the moon to get the phone call from Castleford," said Clarkson, who has spent the last three years with Rovers.
"It will be good for me to fit in with these lads and just train with them for a few weeks and see what I can do. I’m really looking forward to it.
"It’s a high standard of training, a very high standard. Everybody’s pushing you, you can tell that already from day one that the lads are always working hard for each other and anyone that’s slacking they pick that up and egg you on a little bit, so it’s a very good standard.”
Clarkson could be a short-term replacement for Castleford second rower Oliver Holmes, who will miss the first month of the new season after undergoing shoulder surgery.