Danny Addy is set to miss the rest of Hull KR's Super League season after undergoing anterior cruciate ligament surgery on Tuesday.
The 27-year-old Scotland international back-rower, who featured in his country's three World Cup fixtures last year, suffered the serious knee injury in the Robins' pre-season friendly clash against rivals Hull FC on January 14.
Addy, who joined from Bradford Bulls in 2016 and subsequently played a key part in Hull KR's immediate return to the Super League via their Championship promotion in 2017, went under the knife on Tuesday.
And he is now facing up to nine months on the sidelines, which will almost certainly see him sit out the entirety of the current campaign.
Head coach Tim Sheens had previously expressed his disappointment at the prospect of losing such a versatile member of his squad.
He told the Hull Daily Mail: 'Danny was more concerned about nailing down a consistent position but unfortunately with his utility tag, he was our Mr Fix It, playing from centre to hooker.
'Not many people can do that. That makes him very valuable to any team, let alone us.
'He won’t be easily replaced. I spoke to him as soon as I found out after the scan, he was still pretty upset.'
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