Frankie Mariano has become the ninth Castleford player to be ruled out for the rest of the season.
The back-row forward, who played only one game in the first five months of the season because of knee trouble, suffered a rib injury in the Tigers' 14-11 defeat at Warrington and deepens what coach Daryl Powell says is the worst injury crisis he can recall in his career.
"Frankie has gone for the season," Powell said. "We think he might have broken ribs and damaged rib cartilage and that's really painful. He needs further checks but he won't play again this year."
Powell has also confirmed that prop Andy Lynch will not play again this season after breaking a leg in May and undergoing hand surgery on Monday.
"His leg hasn't healed as quickly as we thought it might do so we made the decision for him to have the operation on his hand now," he said.
Winger Joel Monaghan (shoulder), stand-off Ben Roberts (foot), loose-forward Nathan Massey (hand), prop Lee Jewitt (knee), winger Jy Hitchcox (knee), full-back Ash Robson (knee) and stand-off Tom Holmes (shoulder) are the other players sidelined until 2017 but centres Ben Crooks and Jake Webster and second-rower Mike McMeeken could be back for Castleford's next match against Wakefield on Sunday week.
Powell says captain Michael Shenton, who has been out with a knee injury sustained in the opening game of the season, has a chance of making his comeback before the end of the campaign.
"We are just taking it week by week with Shenny now," he said. "He is building up his training and starting to do contact work.
"Really it's just a fluid situation with him but we'll wait and see if and when he is right to play. Obviously we need to make sure he goes through all the things that he needs to and we'll make a decision down the track."