Croker, 27, says helping his father Allan on the family dairy farm helped build the habits behind his work ethic.
The family has farmed the same land near Nabiac, NSW, for close to 150 years. Allan is the fifth generation to work it, Croker said, and the pair repaired a headstone from the 1880s marking the first Croker on the farm.
"He has always said there wasn't going to be a sixth (generation), he didn't want us to take on dairying because it's really tough work and the reward is not as much as it was back in the day."
Newcastle coach Justin Holbrook gave Croker the starting No.13 role after arriving in the off-season. Croker went on to play every match in the regular season and finals.
"This year has been my best year personally," Croker told AAP.
"I've worked hard to get this 13 role so I've never wanted to have a day off in case someone comes in. There's that old saying, 'never have a day off work else someone will steal your job'."
Newcastle have risen from wooden spooners to Sunday's grand final against the Sydney Roosters. Croker has won positional contests with Isaah Yeo, Erin Clark and Cameron Murray over the past month.
He will face Victor Radley as the Knights start as outsiders.
"We are that connected as a group, we will do anything for each other. Even when the legs cannot move," Croker said.