"Horowhenua-Kapiti bring a different component than Buller bring.
"They scrummage really well, good in tight. Big, strong ball carriers, so we've got to do more of what we did [last] Saturday."
Currently in eighth place, Horowhenua-Kapiti have an identical record of 3-3 to the teams all the way up to fourth.
They started well with a 32-14 away win over East Coast, their only four-try bonus point, before taking a heavy 52-20 loss to South Canterbury at home.
Kicking saw them to a 33-17 away derby win over Wairarapa Bush and a 25-18 home victory over King Country.
The wheels flew off in Oamaru with an 89-23 smashing by North Otago, but a week later at home against Mid Canterbury, they came back from 15-0 down at halftime to just fall short at 15-13.
Captained by loose forward Ryan Shelford, who played his 100th match for the union this year, the forward pack includes 2017 Heartland Player of the Year prop Scott Cameron and would love to pull Whanganui into a scrappy arm-wrestle.
Then, rather than scoring multiple tries, they could rely on their excellent goal-kicking halfback Jack Tatu-Robertsson to see them home - having slotted 10 penalties and seven conversions this season - while his backups Tyler Tane and Keaton Kawana have combined for two conversions and penalties.
"He's been playing well for them," said Hamlin, of Tatu-Robertsson.
"They've been a mixed bag of late – we've got to get our house in order as best we can.
"Looks like it's going to be a heavy ground with a bit of rain."
Hamlin remembers what that could mean – Whanganui's last defeat to Horowhenua-Kapiti was 15-8 in 2017 on another horrible weather day in Levin when the home pack stifled any attacking momentum and another radar kicker - James So'oialo – slotted three-pointers from everywhere.
"It's about keeping the momentum going. We can't afford to drop a [competition] point, otherwise, we're looking at going to Thames instead of them coming here [for a semifinal].," Hamlin said.
"We've just got to get our job done – win and score four tries doing so."
Key to this will be getting players to the breakdown in rapid order as they did against Buller while working the standout ball-runners into gaps.
The likes of winger Alekesio Vakarorogo, centre Timoci Seruwalu and No 8 Semi Vodosese don't even need a clear path - just set them running on the outside shoulder of their marker rather than directly at the midsection and they'll do the rest.
Needing a big game from the front row group, Whanganui's current curse of injuries at training continued with prop Slade Hay-Horton hurting his calf muscle, which is likely to keep him out for the rest of the campaign.
With Hamlin still not willing to risk an early comeback for Gabriel Hakaraia, this keeps the responsibilities on the four props who did well against Buller – the coach happy with Ranato Tikoisolomone's first start this campaign.
While it will be well strapped, fullback Ethan Robinson's foot shouldn't be an issue after he came off in the 70th minute against Buller.
As midfielder Kameli Kuruyabaki will be attending a family gathering in Fiji, which is why Josaia Bogileka was promoted to the starting XV against Buller, there will be a reserve back spot to fill.
Tiari Mumby and Ezra Malo were bracketed on the bench last week, with Malo getting the nod and coming on to score a try and conversion, while apprentice player Jack O'Leary could also be considered for his second cap.
Kickoff is 2.30pm at Levin Domain.
The Whanganui team will be selected from:
Forwards: Keightley Watson, Tai Pulemagafa, Ranato Tikoisolomone, Bradley Fountain, Roman Tutauha, Jack Yarrall, Ben Whale, Matt Ashworth, Josh Lane, Mason Johnson, Samu Kubunavanua, Jamie Hughes, Regan Collier, Semi Vodosese.
Backs: Lindsay Horrocks, Caleb Gray, Kahl Elers-Green, Dane Whale (c), Tyler Rogers-Holden, Tiari Mumby, Josaia Bogileka, Timoci Seruwalu, Alekesio Vakarorogo, Jack O'Leary, Ezra Malo, Ethan Robinson.
