Cronulla Sharks coach Shane Flanagan will use the opening premiership rounds to determine whether Josh Dugan or Valentine Holmes will be his regular fullback this season after revealing the pair would share the role in Thursday night's local derby against St George Illawarra Dragons.

Dugan was named at centre for the Sharks on Tuesday but he is set to start at fullback against the Dragons in a backline shuffle, which involves Holmes moving to the wing after being targeted under the high ball by North Queensland Cowboys halfback Johnathan Thurston in the opening round.

Flanagan said the pair would rotate between fullback role, as Holmes had previously done with Ben Barba when he was at the Sharks.

Parrramatta Eels used a similar ploy last Sunday, with Jarryd Hayne shifting between right centre and fullback, and Bevan French moving to the wing, while Melbourne Storm did the same when Greg Inglis was playing for the club and he sometimes rotated with Billy Slater during defensive sets.

However, Flanagan said he would eventually settle on one of the pair at fullback and rejected speculation the club's chances of retaining Holmes would diminish if he wasn't wearing the No.1 jersey.

"The media has made more of an issue that Val wanted to play fullback, it is something that he wanted to try but he is a quality player and Val will do what is best for the team," Flanagan said.

"I think it has let the pressure of him a little bit the last few days that he doesn't have to do it all on his own."

Dugan has played right centre in Australia's World Cup winning team but is considered one of the best fullbacks in the NRL, while Holmes scored a record six tries for the Kangaroos in the semi-final against Fiji.

However, Flanagan suggested Dugan needed more match fitness before assuming the fullback role on his own.

"They will share the role tomorrow, there is no secret about it, You can't keep secrets in football," Flanagan said. "I think it will work well, we did it in the trials so it is nothing new.

"They will swap at different stages. Duges is a big body and we don't expect him to play 80 minutes at the level I want him to play at fullback.

"There is a lot of work to be done there so it gives me the chance to flip him on to the centre and move my centre out to the wing."

Dragons coach Paul McGregor told reporters at WIN Stadium on Wednesday that he wasn't concerned where Dugan played but privately the team was anticipating his switch to fullback.

"They are both talented players in whatever position they play," McGregor said of Dugan and Holmes.

"Both are very good players, both run the ball with a lot of ammunition, they have got size and speed. They are both very similar players, they like to run the footy."

Vaughan puts heat on Dugan

McGregor predicted Dugan would be keen to win against his former club but insisted there was no ill feeling between the Test star and the Dragons over his departure.

"He was very good for us over a number of years so he is going to enjoy playing against his old teammates and old coach," McGregor said.

"As a professional sportsman, you feel that you know your own worth and with Josh he felt that he required a certain amount of money so he moved to a club where he got what he needed and I wish him all the best, except tomorrow night."

While he expects Dugan would provide Sharks coach Shane Flanagan with inside information about the Dragons' playing style, McGregor said they know how he plays.

"You know his habits, there is no doubt about that but you have got to stop him, you have got to stop the things he is good at and try to expose the things he is not so good at," he said.

"That is the same with every other player but you do know a bit more about an individual when you have coached them for a number of years."

Flanagan said he spoke to any new player when they first went up against their former club to ensure that their focus was solely on the Sharks and he would talk to Dugan before the Dragons clash.

"He has been excited but we need to make sure he doesn't get too excited and he plays his game properly," Flanagan said. "It is a challenge for him to handle all of those emotions, it is a big game and hopefully we get the best out of him."