The Australian No.7 jumper is up for grabs after star halfback Johnathan Thurston added his name to the growing list of Four Nations withdrawals when he succumbed to an ankle injury on Wednesday.

Thurston was one of four players to pull out of next month's tournament at Wednesday's medical, joining centres Michael Jennings and Jamie Lyon (both ankle) and Gold Coast backrower Mark Minichiello (groin) in failing to prove his fitness.

His withdrawal leaves the likes of Scott Prince and incumbent Cooper Cronk - who played in the May Test against New Zealand when Thurston was unavailable - as front-runners to line up in the halves alongside skipper Darren Lockyer, while Sydney Roosters playmaker Mitchell Pearce could also force his way into the side with a strong performance in Sunday's grand final.

Thurston suffered ankle syndesmosis in his side's round 22 loss to Brisbane last month, but had hoped to be running by this weekend.

Instead, he will have surgery to remove a screw in his ankle later this week - Australian coach Tim Sheens admitting his loss was a blow on top of the unavailability of other first-choice stars such as Greg Inglis and Justin Hodges.

"He doesn't want to let anybody down, let alone his teammates, his country or himself," Sheens said of Thurston.

"A little while back he was talking to me and he was hoping to be (available) but with the cast off and scans and things it just hasn't healed as much as he was hoping."

Prince hasn't played Test football since 2008, but was hoping to get another chance to impress before Gold Coast's promising season ended with a whimper against the Roosters last Friday night.

"It (Thurston's injury) has taken a halfback out of the equation so there's two remaining teams in the competition and the selectors I'm sure will have their eyes on a number of players in that, so we'll have to wait and see," Prince said.

"I've been given an opportunity in the past and I haven't let anyone down I hope."

While there may be plenty of back-ups in the halves, the options in the centres are thinning by the day with Jennings and Lyon joining the injured brigade.

Currently the only specialist centres in the train-on squad are veteran Brent Tate and Willie Tonga, as well as uncapped duo Chris Lawrence and Jarrod Croker.

Sheens admitted the dearth of centres had opened the door for St George Illawarra pair Mark Gasnier and Matt Cooper to force their way back into the green and gold, with the Kangaroos mentor worried over the lack of experience within his group.

"All four from last year's Four Nations are out and Jamie so that's five centres from the last five Tests, so that's again an area where we will be tested," Sheens said.

"I'm loathe to go too many young blokes, the selectors may have a different thought, but with us losing so much experience and so many key players, I can't afford to go and throw a lot of young blokes in either."

Having made a miraculous return from a broken jaw to play in the finals series with the Tigers, Lawrence said he was relishing the prospect of representing his country.

"There's definitely an opportunity there for me," he said as he watched Wednesday's training session.

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