New Zealand was patient in the first half, and this factor, as much as anything, will have pleased head coach Chris Boyd. The gaps in the Samoan line gradually widened, and Vince Aso carved through on a long burst to set up Mitch Drummond for a sweet try.
New Zealand also had the obvious advantage of having no less than three players who were more than comfortable slotting into first receiver, and either the accomplished Richie Mo'unga or his replacement Simon Hickey plus McKenzie were able to eat up easy tactical metres with their boot. Lock Geoffrey Cridge was the prime ball winner at two in the lineout, and it was a drive off his clean take that led to Matt Peni's score against his 2013 JWC team. The Wellington No 8 was a handful with his bullocking carries and he set up some swift phase ball for New Zealand.
Samoa, who had been very competitive, if not accurate, for most of the first half, clawed back into the contest on the stroke of halftime when No 6 Joe Lee slid over after captain and flanker Henry Stowers had made serious yards.
It was a critical try but it appeared to galvanise Samoa more than New Zealand. Hooker Leif Schwencke, from Auckland's Suburbs club, ripped into his work in an energised performance, and was in the thick of a Samoan scrum. No 8 Richard Mariota also gave a good account of himself.
Peni was at it again in the second spell, heading hard and straight to set up Garden-Bachop's second try, the final pass delivered by McKenzie.
Samoa was not finished and when centre Nathaniel Apa dived over in the corner, there may have been some alarm bells ringing in the New Zealand camp, especially as Samoa now had the lion's share of the ball, the field position, was putting on scrum heat, and winning penalties from Argentine referee Federico Anselmi.
Had Apa cleanly latched on to an intercept pass from McKenzie with 10 minutes to run, who knows what may have transpired?
Instead Tevita Li cut a wicked angle to scorch in from 40m and it was game, set and match.
Anton Lienert-Brown and Kyle Harris put late exclamation marks on the win.
New Zealand (J. Garden-Bachop 2, M. Drummond, M. Peni, T. Li, A. Lienert-Brown, K. Harris tries; R. Mo'unga pen 2 con, Simon Hickey 3 con). Samoa (J. Lee, N. Apa tries; W. Talataina-Mu con). Halftime: 22-7.
New Zealand 48
Samoa 12