Lock Gavin Thornbury had it over King Country's well respected captain Aarin Dunster and pinched at least four lineouts off their throw, while 6-7 times Wanganui trapped attackers in the maul and therefore received a scrum, something the home side could not do to them once.
Captain Peter Rowe made good tackles when it counted, as did young winger Te Rangatira Waitokia and fullback Ace Malo, especially in the second half as previously quiet King Country second-five John Koko and fullback James Hemara were suddenly everywhere.
Reserve backs Whakataki Cunningham and Alex Thrupp also threatened to cause havoc, and it was Cunningham who fired King Country's last shot as he stepped through tacklers and dived under the posts with two minutes left, yet lost the ball and allowed Wanganui to clear their decks.
Moments beforehand, Wanganui had got a penalty 30m from King Country's line and although coach Jason Caskey would have preferred the side back their dominant lineout by kicking to touch for a rare tryline attacking opportunity, Rowe opted to have reserve first-five Dane Whale land their only points of the stanza to make a draw unlikely if King Country would finally crack a second try.
Caskey could see why the home side took the gamble to run their entire bench on just after the break.
"They probably needed to. Down 20-0 playing against the conditions, trying to get yourself back into it.
"She's a couple of different halves.
"At halftime we talked about not giving away the penalties to them, yet we gave away four in ten minutes.
"We stopped playing rugby, when we got the ball we were trying to hang on."
Caskey had still expected a tight clash so was very pleased the pressure at the lineout and the turnovers in the maul meant while King Country dominated second half territory, they could not keep momentum for long enough periods to score more than their one try.
"We've done a lot of work on their lineout in the week and it worked a treat.
"If you can take half of their set ball off them, it helps."
Rowe said the team had not lifted when they saw they were taking on so many fresh faces.
"We came out flat. I hate halftime sometimes, I wish we could have just turned around and carried on.
"You saw our line speed stopped and we were just happy to make tackles."
He also praised the forwards for cutting King Country off in the lineouts and the breakdown.
"It's good if you're doing that, that you make those things count."
Other standouts were Thornbury's partner Campbell Hart, while tryscoring halfback Lindsay Horrocks kicked very smartly in the second half when he found himself lacking for ball-runners.
Surviving an early attacking chance from King Country winger Dean Church, Wanganui worked swiftly into attacking position and would leave spare forwards out wide to hit the line on the fringes.
It worked as Waitokia sprinted into a gap and found hooker Roman Tutauha, who showed good toe down the touchline before popping the ball back to Waitokia, who stepped Hemara and dived over in the eighth minute.
Wanganui stayed on attack but spilled the ball at crucial points, while King Country had done their homework on Kuruyabaki and did not give him room to move.
Following a penalty scrum, Horrocks took the pass from No8 Renato Tikoisolomone and backed himself drive through two tacklers and get the ball down.
Tikoisolomone continued to redeem his earlier fumbles when he claimed a high bouncing ball from behind King Country's posts to score after Wanganui first-five Steve Crosbie charged down his opposite Kieron Rollinson's kick, although he then missed the straight forward conversion.
If observers were puzzled when Cunningham replaced Rollinson only six minutes after resumption, they would have been shocked when all four reserve forwards ran on at the very next stoppage, while the remaining two back reserves jogged out only two minutes after that.
Halfback Zayn Tipping had just added a penalty in front on King Country's first real attacking chance, and they suddenly exploded with fresh legs carrying them right back into Wanganui's half.
Hemara broke through down the far touchline and found Church, who popped it back to Hemara to scoot out of the last diving tackle and score a very good try for 20-10 after 55 minutes.
But for the next 20 minutes, King Country would attack constantly but ultimately come unstuck through Wanganui turnovers or their own bad passes, although the visitors kept presenting further opportunities as they could not get out of a defensive mindset.
Whale coolly added further breathing space in the 74th minute, but similar to last weekend, Wanganui could not gather the kickoff and King Country had a chance to score quickly, which was denied when Cunningham couldn't hang on at the line.
Wanganui 22 (Te Rangatira Waitokia, Lindsay Horrocks, Renato Tikoisolomone tries; Steve Crosbie con, Dane Whale pen) bt King Country 10 (James Hemara try; Zayn Tipping pen, con). HT: 20-0.