Queensland's inability to declare Carl Webb a certain starter for Wednesday night's Origin opener suggests all is not well with their forward juggernaut.

Webb, Queensland's intimidator, broke down at training on Sunday afternoon.

An MRI scan on Monday was expected to eliminate concerns a minor hamstring strain would prevent his ripping into the Blues in the opening game of the Origin series at Suncorp Stadium.

But with the Maroons medical staff delaying a decision for another 24 hours the odds of Webb playing lengthened a little.

Team doctor Roy Saunders refused to comment on the result, adding to speculation Webb's injury may be worse than first thought.

While the Maroons were keeping their cards close to their chest, Webb told his NRL club North Queensland that he was confident of not only playing on Wednesday night but also backing up for the Cowboys 48 hours later.

North Queensland chief executive Peter Parr admitted he was "concerned" by Webb's hamstring complaint but said the Cowboys enforcer remained positive about the prospect of playing two games in three days.

The Cowboys tackle the Bulldogs at Suncorp Stadium on Friday night.

"I have spoken to Carl at length today and he was confident of taking the field on Wednesday night and thought he would be able to back up on Friday night," Parr told AAP.

"He said there was a little niggle there but the scans were more a precautionary thing.

"So in his own mind he was confident of being able to get through both games.

"From my conversation with Carl, he didn't consider himself to be in any doubt."

The 26-year-old Cowboys hard man will have a fitness test when Queensland go behind closed doors for their final training run at Suncorp Stadium late on Tuesday.

Melbourne Storm powerhouse Antonio Kaufusi, who made his debut for Australia against New Zealand earlier this year, is on standby although rookie Neville Costigan will go into the starting pack if Webb is ruled out.

There's been talk all week Costigan may start ahead of Webb anyway to utilise his early aggression, rather than have him sitting on the bench expending nervous energy.

Skipper Darren Lockyer, who said his injured right ankle was 98 per cent, said if Kaufusi was called upon, he would handle the big occasion.

"Lang Park, playing for Queensland in front of a packed house, it doesn't get much better than that," he said.

Queensland's odds will drift on Tuesday if Webb is ruled out.

Apart from the fear factor he generates, his loss would upset the forward rotation plan and provide NSW with a mental lift.

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