"It's an important game but I thought it was important to capitalise on the energy the Roosters boys had and the momentum they created for themselves over the last little period," Kearney said.
One of those is Williams, who has been the talk of the World Cup even before the tournament has kicked off. It's something he's been used to throughout his career, and he handles the attention well, but the player is determined to fit in with the team.
"I just do what I do, keep it humble, work hard, do all my extras, tick all the boxes and try to gain, first of all, my teammates' respect by doing all those things you don't see on TV and everything that happens above that is a bonus," he said after training in St Helens.
"This week [against Samoa] will be no different. I'll try to base my game on hard work."
It will be exactly what Kearney wants to hear. The Kiwis' coach has built a simple game plan based around solid defence, completing sets and a low penalty count. It doesn't mean players will be restricted in what they can do, especially someone like Williams who can make the audacious look routine.
"It's quite obvious the talent he has but I think he brings a bit more than that," Kearney said. "He brings a sense of confidence to the people around him.
"I could talk about the intricacies of his talent and what he can do with the footy but, in essence, he has a job to do in this team and understands his role. For a guy of his stature, he understands that he has to get down and dirty sometimes and that's a good quality to have."
Williams will play in his usual position on the right edge, meaning captain Simon Mannering will play down the middle as a back-rower. Elijah Taylor will provide back-row cover off the bench and he will also see action at dummy half if hooker Issac Luke needs a spell.
Thomas Leuluai has been struggling with a sore groin and won't be risked against Samoa. Scans have shown there's no tear or strain and there are hopes a cortisone injection he received earlier in the week will help settle the injury and see him fit to play next weekend against France.
Samoa are considerably weaker than the side many expected them to field at this World Cup with the likes of Roy Asotasi, Steve Matai and Jeff Lima missing but Kearney has still labelled it a "red flag" match.
"I don't buy into any of that talk [of them being weak]," he said. "For me I look at their side and who they have, like Reni Maitua, Anthony Milford and David Fa'alogo rather than who they don't have."