"We went down to Ashburton last year, fell into a hole, got ourselves out, then in the last minute gave away a try," recalled Hamlin.
Training away from Cooks Gardens in order for the muddy field to stay in the best shape possible for Saturday, the team has welcomed back prop Gabriel Hakaraia after finally recovering from his calf injury, while midfielder Kameli Kuruyabaki has returned from his family event in Fiji.
"Gabe's all keen and ready to go," said Hamlin.
"We've had a few illnesses, just the flu. We're getting back to as close as we can be [to a first-string squad].
"It will likely look very similar to what we've had the last few weeks or so.
"It's time to tighten everything up. We can put our plans in place around [facing] a good quality team.
"They seem quite a physical side - it's a perfect dress rehearsal for the following week.
"We can use this as a real springboard to how we want to play it."
Mid Canterbury struggled into their campaign with a 34-29 away loss to Buller and a 36-34 defeat at home to East Coast, both games they could have won.
A 48-15 home win over West Coast built momentum, and then they created history with the first "Golden Point" victory in Heartland rugby – beating neighbours North Otago 40-35 away.
On the road back-to-back in the North Island, a 34-22 loss to King Country stung, before just hanging on 15-13 against Horowhenua Kapiti.
Hamlin got a good look at the side in their 36-13 defeat at home to neighbours South Canterbury last weekend on Sky TV, with the home side right in it at 18-13 after 52 minutes.
Winger Raitube Vasurakuta, who was involved in a controversial try in Whanganui's loss last year, and midfielder Isireli Masiwini have been their top try-scorers this year, while first-five Nathan McCloy shares the kicking duties with regular points scorer Tom Reekie.
Prop Adam Williamson knows his way to the tryline if the pack gets in behind him.
The visitors are in a similar situation to where Horowhenua-Kapiti were last weekend in Levin, so Hamlin will be looking for a little bit more of a secure performance than that 49-28 win.
"The boys know when they haven't played as well as they would like.
"We pointed out a few incidents, a few situations, we could address better.
"If we're not adjusting to what's in front of us, we'll make life harder.
"Our kick receives have been really good, but we gave up two opportunities on Saturday and HK took advantage."
Kickoff will be 2.30pm, with the match also live on Sky Sports 2.
The Whanganui team will be selected from:
Forwards: Gabriel Hakaraia, 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, Kameli Kuruyabaki, Josaia Bogileka, Timoci Seruwalu, Alekesio Vakarorogo, Jack O'Leary, Ezra Malo, Ethan Robinson.
