Thirroul drew level with Helensburgh at the top of the Illawarra Coal League ladder with a gritty 20-14 win over their northern rivals at Gibson Park on Saturday.
Skipper Nathan Fien played a leading hand in the victory along with the recalled Ty McCarthy, who filled in for regular No 1 Sam Clune with aplomb, causing the Tigers endless headaches throughout the afternoon.
Two tries in nine minutes after the half-time break sealed the match for the Butchers, who led 10-8 at the break on the back of tries to Damien Blanch and Sam Coster.
The loss, just their second of the season, snapped a seven-game winning streak for the Tigers, who looked out of sorts for the first time since suffering a 30-14 loss to Wests in round four.
The Butchers now sit level with the Tigers on 19 points, three clear of nearest rivals Wests, who sit in third place leading what is now a chasing pack.
Fien said the Butchers made it hard on themselves after kicking ahead 20-8 early in the second half.
"We played some good footy but we probably invited them back into the game with some of our discipline and a few errors," Fien said.
"We wanted to start the second half fast and we did that but we probably started forcing things a little bit and getting a bit excited.
"They're a class act, they're leading the comp and they nearly made us pay in the end.
"We've got to learn from that but I'm pretty happy. It was a really good win today."
It was the Tigers who jumped out of the blocks quicker when Azan Turoa pulled down a well-weighted kick from Jarrod Boyle to open a 4-0 lead.
Turoa was caught napping minutes later at the other end when Blanch snuck down a blindside for a try from dummy-half to level up at 4-4.
Both sides struggled to break the deadlock until Fien produced a brilliant flick pass to put McCarthy into space with Coster supporting up the middle to finish under the posts.
Thirroul led by six before Stewart Mills hit back for the Burgh to cut the lead to two at 10-8.
The Butchers burst out of the sheds after the break with Jay Gallaghar and Brent Grose both scoring tries to extend the lead to an ominous 20-8.
The Tigers appeared disjointed in attack but gave themselves a sniff when Mills crossed for his second with 15 minutes to play to cut the lead to 20-14.
Helensburgh pushed hard for the leveler but without regular No 7 Eamon Hillen, lacked their normal composure allowing the Butchers to defend their way to victory.
Elsewhere, Wests fought out a 26-20 victory over Dapto while Collegians snapped a three-game losing streak with a 38-20 win over Corrimal.
In the NSW Cup, the Illawarra Cutters were involved in a thrilling 24-24 draw with Canterbury at Belmore Sportsground on Saturday.