Thurston said Cronk, who rolled his ankle at training on Friday, had earned the right to be given until the last minute to prove his fitness.
Queensland doctor Matt Hislop said precautionary scans on Cronk's injury were encouraging and it was hoped aggressive treatment would ensure the half-back was ready to play New South Wales.
"The scans have come back and they have been pretty positive but we will just put him in cotton wool for the next few days," Thurston said.
"We have got players who can fill a role if need be.
"But he [Cronk] has earned the right to be given until the last minute [to prove his fitness].
He admitted Queensland's preparation would be hindered without Cronk despite Thurston's Cowboys team-mate Michael Morgan slotting into the Maroons halves at training.
"It's a bit disruptive but we will have to deal with it," Thurston said.
"It's a pretty important position and he is the best at getting the boys around the park."
Daly Cherry-Evans is in camp on standby to replace Morgan as the new bench utility.
Meanwhile, Thurston said he was recovering well from his hip complaint suffered in last week's NRL win over Brisbane and would begin contact work on Sunday.
Queensland fly out for Sydney on Monday.