The Dragons back five, one of the most open backlines in the NRL in terms of competition for spots coming out of the pre-season, won't be determined until the respective candidates have been tested in match conditions.

St George Illawarra assistant coach Ben Hornby, who primarily looks after the edge defence and catching for the backs at the Red V, told NRL.com that even the vexed position of fullback wouldn't be settled until after the Charity Shield on 13 Feb and an away trial against the Warriors the week after.

NSW Origin fullback Josh Dugan has said publicly on several occasions already this pre-season he is keen to make his mark as a centre, with the only other real candidate for the No.1 jersey being Storm recruit Kurt Mann. The returning Adam Quinlan has been tried there before while utility back Peter Mata'utia has also played there.

Bulldogs recruit Tim Lafai presumably wasn't brought over to play reserve grade so appears likely to nab one centre spot, though if he ends up partnered with Dugan that places a huge question mark over 2015 breakout star Euan Aitken.

The one position that is beyond doubt is Jason Nightingale on the right wing, with the other flank to be contested by Mata'utia, Kiti Glymin and new recruits Kalifa Faifai Loa and Taane Milne, most of whom can also play centre.

Hornby told NRL.com that with all the backs training well and the new recruits impressing, much would depend on the pre-season games.

"The trials are going to dictate who plays where so [Mann and Dugan] will both get a shot at both positions (centre and fullback) and we'll pick the best side for Round 1," Hornby said.

Hornby added there were no particular frontrunners for any of the vexed positions at this stage.

"It's always hard in training, everyone looks good at training so we've got to get out there in the games and make it happen in the games," he said.

"I know the boys are really looking forward to the trial matches. We've got Charity Shield [on 13 Feb] and New Zealand [Warriors, at Nelson on Feb 20] so we've got some pretty decent hit-outs."

Hornby welcomed the versatility provided by having so many players who could fill multiple roles in the backline.

"That's something we've really tried to get this year. We've got blokes who can play different positions and both sides of the field as opposed to blokes who can just play one position. As the season goes on you usually do get injuries so if you've got blokes who can move around it's a huge benefit to your squad," he said.

Asked about the new recruits in particular, Hornby added: "They've been really good; Kurt's been really good, he's training really well, he's fit and looking good at the back there. Timmy's just come back into training the last couple of weeks so I haven't seen a great deal of Timmy yet but I'm looking forward to seeing how he plays and we've got some young kids up from the 20s as well as Taane Milne from the Roosters so we've got some good young kids there.

"Our backline's really strong so we've really got to use it the best we can this year. We really want to keep our defence strong and hopefully we can build on our attack and start scoring some points with those guys.

"Charity Shield's a big game for us every year as it is for Souths and we play New Zealand in New Zealand the week after so they're going to be difficult to play against. We'll get a good gauge of where we're at after those two games and look forward to Round 1 after that."