Ahead of Thursday’s home clash with Castleford, Hull coach Brett Hodgson said: “Unfortunately for Joe and us as a team it is worst-case scenario, he has ruptured his Achilles.
“It’s disappointing because he was performing exceptionally well. It’s going to be a big gap to fill. He’s upset but we’ll get around him and make sure we support him.
“Josh’s medial ligament has fully detached in the tackle. It was quite a nasty tackle to be honest. I don’t think there was any intent from their player to hurt Josh, but the way he fell on his knee, it’s not surprising that it is pretty bad.
“He’s absolutely devastated in the fact that he can’t get out there and perform. Again, we’ll support him and make sure he’s good to go next year.”
The 23-22 result at the weekend was a first win in five matches for Hull, who moved up into the final play-off spot with a win percentage of 53.13.
Hodgson’s men face a Castleford side lying eighth with a win percentage of 50 and looking for a fourth successive victory after beating Leeds, St Helens and Wakefield in their last three outings.
The Australian said: “We knew the importance of that win (against Hull KR), it was good to get that monkey off the back after performing okay over a number of weeks but not getting the results.
“We’ve spoken about the importance of this game again. We’re playing a very good team who have won three on the bounce, so we can’t afford to have a comedown, of energy or effort or attention to detail. We’re prepared well again.
“We’re going into a very tough contest against Castleford, we know that they’re nipping at our heels and want to take that position at the back end of the top six as well. So in effect it’s probably a semi-final come early, and one we’re looking forward to.”