Queensland star Cameron Munster must pass stringent concussion guidelines if he is to play the State of Origin decider in Brisbane.

The Maroons five-eighth will be monitored over the coming days for concussion symptoms after copping a heavy knock just two minutes into Wednesday night’s loss to NSW in Sydney.

He is now in doubt to play Game III at Suncorp Stadium in six days’ time, given the turnaround time.

Queensland’s team doctor Matt Hislop took to Twitter to clarify reports Munster had failed a head injury assessment, saying his ‘category 1’ symptom of poor balance meant he was unable to return to the field regardless of his HIA results.

Category 1 symptoms include loss of consciousness, no protective action in falling to the ground, confusion and disorientation and motor incoordination.

After whacking his head into the ground as he took a kick in goal, Munster struggled to get to his feet and fell over twice before he was helped from the field.

Hislop said Munster passed the HIA which includes a series of questions in the medical room, but his ‘cat 1’ symptoms after the hit were enough to rule him out of the game.

Munster will now need to pass a six-stage concussion protocol with no setbacks to be cleared to play.

“Players are rested and monitored for signs of deterioration,” Hislop Tweeted.

“A repeat SCAT 5 is performed and if passed a graduated return to play is commenced.

“Prior to starting contact a player must pass an additional computer based cognigram test.

“The NRL have clear guidelines on safely returning a concussed player to sport.

“Thankfully most ‘simple’ concussions resolve completely within 7-10 days (in adults).”

Importantly, Queensland coach Wayne Bennett said Munster appeared “fine” in the sheds following the game.

Bennett said he’s hopeful Munster will be cleared to play on Wednesday night, while Ben Hunt will be on stand-by to fill in at No.6.

“All indications are that he’s fine. He has no history of head knocks, which helps,” Bennett said.