Queensland coach Kevin Walters says Cooper Cronk will be given until game day to prove his fitness for Wednesday night's State of Origin opener in Sydney.
Cronk has arrived at ANZ Stadium with the Maroons' team to train for the first time since rolling his ankle on Friday in camp on the Gold Coast.
But Walters said no matter what happened at training on Tuesday, a final decision on Cronk's fitness would be made on Wednesday morning.
The Cowboys' Michael Morgan is on standby to slot into the halves for Cronk, while Warriors forward Jacob Lillyman is expected to be added to an all-forwards bench if the Melbourne No.7 is ruled out.
North Queensland back-rower Gavin Cooper has been drafted in as 19th man.