Kahui's dysfunctional shoulders - he has had four operations in six years - means he could have soreness in that area for the rest of his career, a fact he has acknowledged with his signing for Toshiba in Japan and the relinquishing of a place in the All Blacks at the age of 27.
Not surprisingly given his problems, his confidence is yet to return but there is much to look forward to, including an imminent call-up for the Chiefs which is something he would cherish after missing out on so much last year.
With the Chiefs preparing to play the Stormers in Cape Town on Sunday (NZT), Bundee Aki nursing a bruised thigh, and fellow midfielder Andrew Horrell returning from a stress fracture of the foot, coach Dave Rennie has put Kahui on standby.
However, a more likely return for Kahui will be when the Chiefs get back from their trip to the Republic after playing the Southern Kings in Port Elizabeth next weekend - a mouthwatering replay against the Highlanders in Hamilton on March 22.
"I've done a fair bit of contact over the last couple of days and I'm starting to feel better after every day. Every tackle I make makes me feel more confident," he said.
"Initially when I first started doing the contact stuff I felt a bit of pain, but as I do more the pain is getting less and the inflammation is lessening as well.
"I've been through the process before and I know what it takes to get back to a place where you're pretty comfortable. At the moment I'm doing baby steps but as time progresses ... I know I've got a shoulder that's still recovering but I know it will be good enough and strong enough to play footy."
Kahui, who would have played more than his 17 tests had his body not consistently failed him during the course of his career, chooses his words carefully when he describes his time on the sidelines as "very frustrating".
His latest shoulder problem dates back to the middle of last year when he was led from the Suncorp Stadium pitch in a match the Chiefs lost to the Reds - one of only four they lost all season.
Triumphs viewed, rather than experienced, aren't the same and he wants the chance to know what winning a Super Rugby title really feels like.
"Obviously you want to be part of it. You don't play rugby to sit on the sidelines but for the past few years it's happened more and more to me.
"I've still got to earn a place in the team. They're going pretty well at the moment and Tim Nanai-Williams is showing his full potential which is great to see and the more time Charlie Ngatai gets on the field you'll see his talents as well."
Kahui's fightback has been a lonely one at times - the two hours a day in the gym attempting to keep his weight down and now being left behind while the Chiefs are in South Africa.
But the end is in sight and, with his general fitness up there with the best it has ever been, the chance to test himself can't come quickly enough.
"The first game will come as a shock, you can do as much as you can to prepare for it, but it will still be shock until you get used to the speed of the game again."
Chiefs team to play the Stormers at Newlands in Cape Town on Sunday (4.05am NZT): Gareth Anscombe, Lelia Masaga, Tim Nanai-Williams, Charlie Ngatai , Asaeli Tikoirotuma, Aaron Cruden, Tawera Kerr-Barlow, Liam Messam, Sam Cane, Tanerau Latimer, Brodie Retallick, Craig Clarke (c), Ben Afeaki, Mahonri Schwalger, Pauliasi Manu. Reserves: Hika Elliot, Ben Tameifuna, Michael Fitzgerald, Nick Crosswell, Augustine Pulu, Andrew Horrell, Patrick Osborne.