Thirroul has pulled of a major coup, securing former Penrith, South Sydney and Wests Tigers prop Tim Grant to play in the Illawarra competition next year.
After more than a decade in the NRL, Grant suffered a major pectoral muscle injury last year and retired after 196 games.
Trent Waterhouse, another former Penrith and Butchers forward, had been involved in the talks to bring Grant to the region.
"We're really excited to have him," Thirroul president Brett Jones said.
"He's a big, powerful forward, who'll be able to lead or pack with Damian Sironen.
"And he's a great trainer who has come straight out of the NRL, he's going to be able to set a great example for our young guys coming through."
The Butchers have lost veteran Joel Ruskin and star hooker Joel Johnson, but Jones said they would look at making a couple of other key signings before the new season.
Jones was also extremely confident in a number of their under 18 premiership winners making the step up to first grade next year. Grant was hurt in the Panthers' victory over Manly in May and ended his contract with the club the following week. He made his NRL debut in 2007.
"Tim has been a true professional that our younger players have been able to learn from," Penrith coach Ivan Cleary said after Grant made the decision.
"He demonstrates a 'team first' and 'club first' mentality."
The Butchers finished on top of the Illawarra ladder last year but were knocked out in the preliminary final.
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