Thirroul all but sewed up a top-two spot on the ladder with a 42-24 victory over Dapto at Gibson Park on Saturday.
The result keeps the Butchers three points clear of third-placed Wests, who they meet in the final round of the regular season, and barring a monumental upset at the hands of win-less Corrimal will cement a top-two spot in the penultimate round.
It leaves Thirroul level with competition leaders Helensburgh on 21 points after the Tigers thumped Corrimal 50-14 on Saturday.
The win also gives the Butchers a sniff at the minor premiership should Tigers drop their home match to Wests on Saturday.
After scintillating performances in the past month, the Butchers were far from their best against a willing Dapto outfit but the class and experience of skipper Nathan Fien and fullback Brent Grose, who was shifted into the No 1 jersey in the absence of both Sam Clune and Ty McCarthy, proved the difference.
Grose scored a first-half try and was instrumental in two others for winger-cum-centre Reece Jaeger before Fien produced a brilliant 40-20 and try on the half-time siren to give the Butchers the 20-8 lead.
Fien then sent a pinpoint long ball for Damien Blanch to score barely 30 seconds after the resumption to extend the lead to 26-8 before limping off soon after with a corked thigh.
Dapto kept in the game through two tries to James Ralphs. Jamie Dunning, Jake Goody and Dillon Capaan all scored tries to stay in touch with the Butchers but late four-pointers to Sam Coster and Pat Franks sealed the result.
"We got the job done ... we get the week off next week to freshen up and it's come at probably a good time for us," Fien said.