Kearney was also worried about how Marshall would react and whether it would affect his passion for the Kiwis.
"That was a concern on my part. He remains an integral part of the team and is a member of the senior leadership group and his input is still very much valued. That was a worry but he told me he's committed to what we are trying to do. He understands it's a decision I have made with the team's best interests at heart. In terms of his disappointment, he's not going to hide that but he's a big lad. He's overcome hurdles before. His focus now is on performing and doing well so we can retain the World Cup."
Marshall was a hugely influential figure at the last campaign in 2008 and was again to the fore when he captained the Kiwis to the 2010 Four Nations title but his form for both club and country has been patchy over the past two seasons.
Kearney wanted to take some of the burden off his chief playmaker in the hope he will be back to something close to his best at the World Cup.
He has no such concerns over Mannering, who will step up from the vice-captaincy he held last year.
"It was an agonising decision and one I took a lot of time over,'' Kearney said. "Every time I was thinking about a suitable replacement, Simon just kept coming to mind. It was a no-brainer from my point of view. He's a well respected individual in the rugby league community, has played 30 tests and every time he plays for the Kiwis he delivers.''
Mannering, who has been Warriors captain for the past two seasons, said he jumped at the chance when asked to take over the Kiwis captaincy.
"A huge honour, not only to be considered for the role but to be actually given it,'' he said. "It's probably the biggest honour you can have in the game to lead your country. I'm looking forward to the new challenges in the new role and looking forward to doing what I can for the team. In my role I just want to put the team first. It's a big year for the Kiwis and we will do everything we can to defend the World Cup.''