Dragons forward Blake Lawrie.

St George Illawarra coach Paul McGregor has placed the lure of a regular place on the competition leaders' interchange bench in front of his rookie forwards heading into Thursday night's clash with Melbourne at AAMI Park.

With Paul Vaughan, Jack de Belin, Tyson Frizell and Tariq Sims on State of Origin duty with NSW, McGregor has called on Jacob Host, Luciano Leilua, Blake Lawrie and Hame Sele for the Storm clash, a contest that could decide whether the Dragons remain top of the table.

A loss in Melbourne would see South Sydney join them on 26 points at the top of the Telstra Premiership ladder as the Rabbitohs have a bye. If St George Illawarra were beaten by more than 15 points they would drop to second on for-and-against.

McGregor has been planning for the absence of his Origin stars, including halfback Ben Hunt, since the start of the season. Host, Leilua, Lawrie and Sele have all been given a taste of NRL action to prepare them for Thursday night’s match.

Host, who started in place of Frizell in last Thursday night's 20-18 defeat of Parramatta, has played three NRL matches, while Leilua has come off the interchange on five occasions and Lawrie and Sele have featured twice each in the top grade.

If the Dragons remain at full strength, there is one position up for grabs alongside Jeremy Latimore, Leeson Ah Mau and Jason Nightingale on the interchange and the rookie quartet will have the opportunity to push their claims for that spot against the Storm.

"We haven't had many injuries this year and certainly the guys who are coming into the game tomorrow night have had a lot of education around their mental approach as well as their physical approach, and there is obviously the opportunity that they can force their way into a football team that is going well in first grade," McGregor said.

"There is a lot of excitement in the shed, with those guys who have been waiting for this opportunity, and they need to go out there and really give their all."

Host, Leilua and Lawrie will start in the back row, while Sele has been named on the bench, along with Latimore, Nightingale and rookie hooker Reece Robson, who has played one NRL match this season.

"We have had a big focus on being ready for the step up when we are needed, putting in the hard yards at training and doing the little things in reggies [Intrust Super Premiership]," Host said.

"I felt pretty comfortable taking Friz's spot and hopefully I can keep the consistency. I just had to mentally prepare myself for the starting role."

Leilua, who made an impact off the bench against the Eels and was only denied a try after video referee Ashley Klein ruled Jarryd Hayne had got a hand under the ball to prevent him grounding it, was told by McGregor to prepare for an 80-minute stint in place of Sims.

St George Illawarra forward Hame Sele.
St George Illawarra forward Hame Sele. ©NRL Photos

"I have just got to be mentally prepared and get my head around starting," Leilua. "I would love to get a starting spot but Mary is going to pick the best 17 each week and as long as I am in the 17 I am happy."

Halfback Darren Nicholls, 29, will make his NRL debut in place of Queensland's Ben Hunt, becoming the oldest player to do so without having played elsewhere at an elite level since Illawarra Steelers fullback Mark Taylor in 1994, according to League Information Services statistician David Middleton.

McGregor questioned the Maroons decision to demote Hunt from halfback to the interchange bench after losing the first two matches.

"I'm happy for NSW because I'm a New South Welshman, but I am certainly disappointed on an individual basis for Benny," McGregor said.

"However, he will do a very good job off the interchange. With Benny coming on in that dummy half, which one would think, he could cause some trouble late in the game.

"It gives Queensland a different dimension but I still feel that Benny didn't do enough wrong."

Asked whether the Maroons had abandoned their so-called "pick-and-stick" policy, McGregor said: "Looks like it, doesn't it. They haven't lost for a while so I think losing challenges them in all different areas.”