NRL: NSW Blues in State of Origin disarray with Luke Keary out

NSW's defence of the State of Origin shield have been thrown into disarray with Luke Keary ruled out of contention for game one due to concussion.

Keary suffered his fourth head knock in two years when he was knocked out on Friday night in the Sydney Roosters' NRL defeat to Newcastle.

Blues adviser Greg Alexander conceded coach Brad Fittler would have named the Roosters' star on Sunday in his team.

"Luke was looking like he was going to break into the team but I don't think Luke will take part. He won't be fit for game one," Alexander told ABC radio on Saturday.

His absence opens the selection door for South Sydney halves Cody Walker and Adam Reynolds, as well as incumbent James Maloney from Penrith.

Nathan Cleary, after performing well on Thursday night, is widely tipped to keep his No.7 jumper despite the Panthers' horrid start to the NRL season.

However, Keary's scratching might force Fittler to opt for the club combination from the Rabbitohs, who face the Wests Tigers on Saturday night.

The concussion is a cruel blow for Keary, who is arguably the form player of the league following on from his Clive Churchill medal display in last year's decider.

The back of his head bounced on the turf at McDonald Jones Stadium after being bullocked by Daniel Saifiti in the eighth minute.

He momentarily lay prone before staggering from the field.

His latest concussion comes five weeks after also being forced to miss the club's traditional Anzac Day clash due to a head knock.

Roosters coach Trent Robinson described Keary's health as "average" after the game, and said the 27-year-old would be unlikely to train until Tuesday.

"They can't do contact until day four, I think it is. They've got to make sure that they don't have headaches (the next day)," Robinson said.