Cowboys outside back Enari Tuala.

For three years the composition of the North Queensland Cowboys centres was not up for debate, but that is set to change with at least six candidates in the mix for 2019.

Justin O'Neill arrived at the club in 2015 and his partnership with Kane Linnett since that premiership-winning year was a constant and successful one prior to the woes of 2018.

A pec injury curtailed Linnett's 2018 season. He has since joined Super League club Hull KR on a three-year deal.

O'Neill remains on deck after taking up a one-year option following an indifferent season which saw him dropped to the Intrust Super Cup.

The Cowboys brains trust hopes he can return to the form that saw him selected for Queensland and Australia in 2016.

Even if he does, there are no guarantees for the other candidates in a position sure to be hotly contested.

"The centre position is up for grabs at the moment and it is certainly not going to be handed to anyone," Cowboys assistant coach Josh Hannay told NRL.com.

"Justin O'Neill is still there, Javid Bowen is training really well and Tom Opacic, [recruited] from Brisbane, isn't the flashiest of centres but is someone I've always had a high opinion of as a very reliable centre.

"There is an opportunity for Enari Tuala if he puts his head down and works hard, and young Dan Russell has got a lot of potential.

"Ben Hampton could potentially make a great strike centre after playing some footy there for us in the season just gone.

This is a really good opportunity for me to push for that centre spot

Enari Tuala

"He is incredibly dangerous with the footy and the one thing that has prevented him from nailing down a position is his versatility ... so there are six guys at least who are all in contention."

Tuala, who hails from Cairns like his hero Justin Hodges, is a 20-year-old centre who was given a crack by coach Paul Green in 2018 in 10 NRL games.

He has also been identified by the Queensland Maroons as a potential Origin player of the future and has been selected in several Queensland under 20 squads.

Hannay said Tuala had impressed when given an opportunity and would keep the heat on next season if he continued to work on his defensive game.

"First and foremost at club level, there is an opportunity for a young guy like Enari if does all the little things right with regard to his diet and preparation," Hannay said.

"He brings to the table everything you would want in a centre. He runs really good lines, has a really good pair of hands and brings the ball back really well from the back-field from kick-returns.

"His attacking game is pretty strong so for him, his focus needs to be to make sure he is a reliable defensive centre so  he can do the job on the edge."

Tuala said he had become more confident as a result of his NRL experience last season but still needed to adapt to the speed of first grade after being promoted from the Northern Pride in the Intrust Super Cup.

"My fitness is something I am working on now," Tuala said.

"I am doing an extra session on Saturdays with a few other boys in the gym and it is paying off.

"This is a really good opportunity for me to push for that centre spot. We have a lot of depth in our squad so there is a lot of competition."