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.
"It's important how he pulls up tomorrow. The swelling has gone down but these injuries take time to heal.
"He only had four days. It's remarkable to get to this position but there won't be any risks taken."
Walters says he has no qualms trusting Cronk with making the right call, and that the Maroons will not be risking unfit players in the crucial series opener.
"He's honest enough," he said.
"In the past, we have taken players who are not quite 100 per cent and it has fallen apart.
"We don't want to fall into that trap."
Cronk began training with the main group but then started sprint drills by himself as staff tried to assess his recovery.
Walters dipped his hat to Michael Morgan, set to step up in Cronk's absence into the halves after excelling at training since the half-back rolled his ankle on Friday at their Gold Coast camp.
Warriors forward Jacob Lillyman will be added to an all-forwards bench if Cronk is ruled out.
North Queensland back-rower Gavin Cooper has been drafted into the squad as 19th man, training on Tuesday with the main group.
Walters was surprised NSW captain Paul Gallen had accused Queensland of playing mind games over Cronk's injury.
"I grew up in Ipswich so we don't know what smoke and mirrors are - we are honest as the day is long," he said.
"To be honest, we don't know if he will play and I am not a betting man."