Cronk surprised onlookers on Tuesday when he ran out with the Maroons' squad for their only training session at Sydney's Olympic stadium ahead of the State of Origin opener.
While he is not certain Cronk would be fit to play, Walters remains confident the half-back would make the cut - but the final call will be left to the man himself.
"I will let Cooper make the call. He is big enough to work out whether he can get through 80 minutes of Origin," Walters said.
"He's quietly confident he can play. But tomorrow, we have to make a decision," he said.