"His numbers weren't always that great," said Kiwis selector Richie Barnett. "Statistically, he was behind the other forwards."
It was one of the reasons why Waerea-Hargreaves was controversially omitted from the 2014 Anzac test - despite the Kiwis being decimated by injury - and he also sat out the triumphant Four Nations campaign later that year, citing fatigue.
Hovering in the background was the cultural change Kearney and the NZRL wanted with the Kiwis and Waerea-Hargreaves voiced his disappointment regarding what he considered a lack of communication from Kearney.
There's confidence he's now ready to make an impact in the black and white V.
"He's the real deal now," said former Kiwi Daryl Halligan. "He has matured. He knows how to get himself up for games and also to listen to instructions. That wasn't always the case."
No one doubts Waerea-Hargreaves' ability but he hasn't always been able to harness his aggression and energy in a good way.
"He was a bit of a loose cannon but I don't see that now," said Halligan. "He can still be the aggressor but can take it as well. He won't fly off the handle. He has learned that he can be the tough hard man without having to show it all the time."
Waerea-Hargreaves credits his turnaround to increased maturity ("fatherhood has helped a lot") and an improved focus.
"I needed to take the emotion out of it and just go out there and focus on myself," said Waerea-Hargreaves. "[It was about] learning to make those emotions effective, instead of ineffective and I've got the balance right so far."
His ruptured ACL - the first serious injury of his career - also gave valuable perspective.
"Over the last 12 months, I've made a conscious effort to be more of a professional athlete," said Waerea-Hargreaves. "It was a physically and mentally challenging injury. You learn a lot from having a big injury and knowing what it takes to get back there."
And it sounds like Waerea-Hargreaves, after almost four years in the wilderness, is ready to unleash in England.
"I've seen all these other young blokes come through [and] it's been a blessing. That's what you want. It keeps the Kiwis squad healthy. [But] watching from the outside, it burns [and] that fire is burning.
"I'm a proud Kiwi. I not only wear that black jersey for myself and my family, I wear it for the whole nation. It's been challenging [so] to be back in the mix is an awesome feeling."