The New South Wales Blues' preparations for Game 3 of the State of Origin series have been thrown into chaos, with set to debut prop Jordan McLean injuring himself at training on Thursday morning.

It's understood he has been sent immediately for scans on a hamstring injury, although it's unclear exactly what severity the injury is at this stage.

McLean was a shock call-up to the 22-man Game 2 squad for NSW coach Brad Fittler, before being promoted into the starting team for the decider, to be played in Brisbane on July 13.

It's understood he is out of the game.

McLean told reporters that the opportunity he had "wasn't to be."

“My career has been full of ups and downs and I’ve kind of been used to it but I thought there might be some light at the end of the tunnel getting this opportunity but it wasn’t to be,” McLean said.

“I still haven’t talked to my family and that’s going to be the hardest thing to tell them I won’t be playing next week.

“When you get your opportunities… I don’t know what’s going to happen in the future at the moment. I’m pretty disappointed.”

His promotion came after a shoulder injury to Payne Haas which will sideline him for a few weeks as he attempts to overcome AC joint problems which have slowed him down this season.

New South Wales are yet to decide on a replacement, but will need to do so in a short timeframe given eight clubs are to play this weekend, and those players will be unable to back-up from club commitments on the weekend to play in the Origin decider on Wednesday.

The Blues only have one forward in the reserves of their 22-man squad in Newcastle Knights' prop Jacob Saifiti, who now appears at short odds to make his Origin debut, although it's likely that Junior Paulo would take starting duties.

GOSFORD, AUSTRALIA - FEBRUARY 29: Jacob Saifiti of the Knights runs the ball in the warm up during the NRL trial match between the Sydney Roosters and the Newcastle Knights at Central Coast Stadium on February 29, 2020 in Gosford, Australia. (Photo by Tony Feder/Getty Images)

Fittler will also likely be able to call further coverage into the squad, with Reagan Campbell-Gillard or Jacob's brother Daniel the most likely options. Daniel played Origin last year, while Campbell-Gillard played Game 1 for the Blues this year.

This is the second scare for the Blues camp, after 19th man Nicho Hynes, who trained with the team on Monday, yesterday tested positive to the coronavirus which will now keep him out of the Sharks' side to play the Melbourne Storm this evening. He has been replaced in camp by Chad Townsend.