Queensland coach Kevin Walters conceded Johnathan Thurston is “very doubtful” for next month’s State of Origin decider at Suncorp Stadium.

Thurston is racing the clock to beat a shoulder injury for what will be his final Origin match for the Maroons, ahead of his representative retirement at the end of the year.

He is still waiting on the results of scans from Thursday, after he re-injured his problematic right shoulder in Wednesday’s 18-16 last-ditch win over NSW.

He will miss what would have been his 300th NRL match on Saturday against Penrith, while North Queensland have been unwilling to put a time frame on his return.

But Walters admitted on Friday the prospect of Thurston playing at Suncorp Stadium on July 12 was highly unlikely.

“He is really knocked around – very doubtful for Game III,” Walters told Triple M Brisbane.

“I don’t know how he got through the game.

“We’re going to try and do everything we can for little Johnny.”

Thurston is one of two serious injury concerns for Queensland.

Centre Darius Boyd has already been ruled out for next month’s decider with a broken thumb, with surgery expected to sideline him for six weeks.

The Maroons have a number of backline options to fill the left-edge position, after Justin O’Neill was dropped from the right side after Game I.

But Walters indicated Melbourne’s Cameron Munster, who was in the Maroons camp as 18th man for Game II, was the frontrunner to make his Origin debut in the spot.

“He’s played some centre at that level – very much respected amongst the group with his defence and the way he goes about his footy.

“So he will be an option for us.”

Walters also suggested bench utility Michael Morgan could also cover the slot, given he filled in on the right and provided the match-winning pass after Will Chambers was taken off with concussion on Wednesday night.

However that would seem unlikely given the way Queensland value the Cowboys five-eighth’s versatility as an interchange.