Merrin is a certain starter for St George Illawarra's annual Charity Shield trial against South Sydney in Mudgee after battling a minor back issue last week.

It will be Merrin's first game back in Australia since leaving Penrith at the end of 2018, but his first for the Dragons since his messy exit three years prior.

"It's like my debut again, to be honest," Merrin said on Friday.

"I've got a few goosebumps, a few thoughts in my head. It's been a while since I played in the Red V, and the Charity Shield. It's very exciting."

When Merrin left Wollongong for the Panthers at the end of 2015, he did so as one of the most accomplished lock-forwards in the game.

At the time, he had won a premiership with St George Illawarra and represented the Kangaroos and the NSW State of Origin team as an 80-minute middle man.

But, at 30 years of age, Merrin has embraced the role of impact player in his second stint under coach Paul McGregor.

"It's different this time around," Merrin said.

"Over my career, you always have your self goals and the way you want to set yourself up. I've done a lot in the game now. My main goal is put the team first.

"Whatever my role is for that, I'll take it with both hands.

"I'll see what Mary (McGregor) wants to put me out there for tomorrow. I'll see what the go is with the staff, but I'll hold on as long as I can on the field."

The Dragons have named their best available line-up for their final hit-out for the season proper, including new fullback Zac Lomax.

The rising star faces a stern test against another new No.1 in Rabbitohs recruit Latrell Mitchell, however Merrin is confident Lomax will prove to be a success.

Merrin and Lomax have roomed together in the build-up to the clash, with the Dragons enjoying a camp in Port Stephens following last week's trial in Maitland.

"He's a great young talent and he's willing to learn, puts his body on the line, and that's what you want for a young bloke," Merrin said.

"He's still got many years of learning and got some great skilful players around him to teach him in that regard. I'm full of confidence.

"He's definitely going to hold his own out the back there."

Australian Associated Press