Both came off in the second half of Saturday’s derby win over Hull KR and head coach Brett Hodgson revealed this morning that the prognosis is not good for either player.
“Unfortunately for Joe - and us as a team - it’s a worst-case scenario,” he said.
“He’s ruptured his Achilles and he’ll go in for an operation on Tuesday and have that repaired.
“It’s disappointing as he’d been performing exceptionally well.
“We’re disappointed for him and for us as a team it’s going to be a big gap to fill.
“He’s upset as you can imagine. But we’ll get around him and make sure he;’s supported.”
Cator, 23, has been in fine form but is likely to be sidelined for up to nine months so will also miss a big chunk of 2022.
Reynolds, meanwhile, has had a stop-start opening to his debut season after joining from the NRL and has been hit by another setback.
“Again, unfortunately for Josh and us, it looks like he’ll need an operation,” added Hodgson.
“His medial ligament was 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 him but the way he fell on his knee it’s not surprising that it is pretty bad.
“He’ll go in for an operation probably next week at some stage and start his recuperation from there.”
The former New South Wales State of Origin player, 32, has had injuries and Covid.
Hodgson added: “He has (been stop-start).
“Through the Covid scenario, which was no fault of his own,
“He’s devastated that he can’t get out there and perform for the rest of the year.”
Hodgson could switch full-back Jake Connor to stand-off and bring Jamie Shaul - who came off the bench at hooker for his first game in 10 months against KR after an ACL injury- back in his main position of No1.
However, given how well Connor is performing at full-back, he also has the option of recalling teenager Ben McNamara at No6.
Up front, Chris Satae returns to help offset the loss of Cator and Mahe Fonua is also in reckoning after being dropped for the derby.