NSW's attacking power has taken a massive hit ahead of next week's second State of Origin clash with Robbie Farah and Michael Jennings both looking unlikely to play the do-or-die match.

Electrifying centre Jennings hasn't trained or played since injuring his calf in the Origin opener in Melbourne, while creative outlet Farah damaged rib cartilage in Wests Tigers' 23-6 win over Parramatta on Monday night.

Both are now in a race against time to be fit for next Wednesday's match, with Jennings particularly pessimistic about his chances.

He faces a fitness test on Thursday with Bulldog Josh Morris his likely replacement.

"I'm not sure at the moment, we'll see what happens, see what the doctor and our physio say and go from there," the Penrith flier told AAP.

"I've still got to do a lot of physio and do a lot of rehab to get it back to 100 per cent."

Farah's injury is a complicated one, with rib cartilage damage sometimes only needing days to clear but if the injury is more serious it could rule him out for several weeks.

And such an injury is not one the Tigers hooker would want to carry into a brutal Origin clash, with one heavy knock to the damaged area likely to cause severe pain.

Farah must resume contact work by Friday or he will be ruled out.

Morris' Bulldogs teammate Michael Ennis is the expected replacement.

"I have never had one of these before so I don't really know too much about it," Farah told AAP.

"I've pulled up a little better this morning than I felt last night. I was up all night icing it and with just a few days rest hopefully I can get back into training later in the week.

"It is a weird sort of pain. It is hard to explain. It just catches me a bit under my ribs there but I can't explain. It just grabs sometimes."

Blues coach Craig Bellamy has given all his injured players a Friday deadline to prove their fitness.

Jennings and Farah are the most serious concerns but several other players are entering camp this week under an injury cloud, including bench utility Craig Wing (hamstring), lock Paul Gallen (shoulder), captain Kurt Gidley (calves) and centre Jamie Lyon (ankle).

Bellamy said he expects his other players to be fine but Jennings and Farah were giving him worries.

"We think Jamie Lyon will be fine, we think Paul Gallen will be fine," he said.

"Perhaps Michael Jennings, Craig Wing and Robbie Farah, they're a little bit touch and go at the moment so hopefully they'll improve in the next couple of days, we'll certainly need them training by at least Friday.

"If they're not training by then we might make some changes, we've certainly got a couple of shadow (players) in there so we'll make those decisions as we go."

The Blues' injury woes have forced them to call up Canberra duo Tom Learoyd-Lahrs and Joel Monaghan as well as Morris as cover.

And Bellamy says any replacements would come from those three players with the exception of Farah, who was injured after the team was named on Monday night.

"Robbie's a little bit different, when we picked the team last night he still hadn't played the game - his rib injury came later in the game, so if he's not improving in the next couple of days we'll bring someone else in."

Bellamy said Ennis would "near the top of the list" if Farah was ruled out.

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