Queensland half-back Cooper Cronk must prove his fitness on Tuesday to play in the State of Origin opener against New South Wales.
The Melbourne Storm star is battling an ankle injury and is in doubt for the clash at ANZ Stadium on Wednesday.
He was expected to be given until the last minute to prove his fitness, but Maroons assistant coach Trevor Gillmeister said the 32-year-old ideally needed to train.
"I think Kev [coach Kevin Walters] said he'll have to train this afternoon," he told The Big Sports Breakfast.
"Anyway, that's the way it is. I suppose another 24 hours make a fair difference, but hopefully he's good to go this afternoon."
Michael Morgan is expected to slot in to Cronk's role if the playmaker is ruled out.
Gillmeister, however, remains confident Cronk will be fit.
"I'm pretty confident he'll play, but I'm no doctor. I think he does everything possible to get himself on the field," he said.
"Late yesterday afternoon, I said, 'How you going?', he said, 'I'm feeling good'. He said the only thing he hasn't done is run.
"He's not limping or anything like that. We'll see what happens."
The Maroons secured a 2-1 series win last year, having had their run of eight straight ended in 2014.
While Cronk's fitness battle has dominated the discussion ahead of the opener, the usual questions have been raised.
Queensland have just two newcomers - centre Justin O'Neill and wing Corey Oates - leading to question marks over their age.
But with captain Cameron Smith, Cronk - if available - and Johnathan Thurston, the Maroons are still armed with some of the NRL's best.
Maroons coach Walters is in his first series, having replaced Mal Meninga.
Wet weather is set to greet the teams in Sydney on Wednesday as the Blues look to make the most of their home-ground advantage.
Led by captain Paul Gallen, New South Wales are relying on a far more inexperienced side.
Half-back Adam Reynolds is set for his Origin debut and five-eighth James Maloney has featured just three times.
Just whether they can contain Thurston and Cronk, or Morgan, could be crucial to the Blues' chances.