Leeds Rhinos forward Jamie Jones-Buchanan has been ruled out for 10 to 12 weeks with a bicep injury.
Jones-Buchanan suffered the injury early in the first half of the defeat at St Helens but played on for the remainder of the half.
Rhinos head coach Brian McDermott said: "It is tough for Jamie as he is only recently come back from an Achilles injury.
"However, it is a mark of the man that he battled through on Friday to help his team despite the pain he was in.
"I am sure he will tackle this set back with the same zeal he approaches everything in life and will come back even stronger."