Manly coach Trent Barrett has vowed to keep knocking on the NRL's door every week to seek dispensation for rookie hooker Manase Fainu to play after centre Matt Wright and five-eighth Trent Hodkinson were forced to share the dummy half duties against St George Illawarra on Saturday night.

Fainu, the Junior Kiwis hooker, is on a development contract with the Sea Eagles and was named to make his debut in place of the injured Apisai Koroisau at WIN Stadium before the NRL ruled that Barrett had other dummy half options in his top 30 squad.

However, Barrett disputes that Wright, Lewis Brown or Jackson Hastings are specialist hookers and he also used the post-match press conference after the 32-8 loss to the Dragons to question why development players cannot be used in the NRL.

"Matty Wright did an outstanding job there in difficult circumstances and Hodko did a good job but I just question the whole idea behind the six development players," Barrett said. "My understanding is they will probably change it next year, but that's not going to help us now.

Match highlights: Dragons v Sea Eagles – Round 15, 2018

"It's going to be extremely difficult for us to make the semi-finals so I'd love to be able to give the 19-year-old kid, who is a genuine first grader, 11-12 weeks of first grade and lead him into a pre-season next year but we have been denied that.

"If we had an out and out No.9 sitting in my top 30 then that would be a different story but we don't."

The Sea Eagles are carrying retired former Test forward Nate Myles on their books as a member of the club's top 30 under the salary cap, while Darcy Lussick was released to Toronto Wolfpack earlier in the season and Hastings will not be considered for first-grade selection.

In addition, the club has been hit hard by injuries and centre Moses Suli lasted just 24 minutes against the Dragons before joining the casualty list with a sternum injury.

On a positive note, centre Dylan Walker and forward Kelepi Tanginoa will return for the Sea Eagles next match against Penrith at Panthers Stadium on June 30 but neither will solve the club’s hooking problem.

"I am going to try every Monday to get him registered and I will keep knocking on the door because I hope they understand the situation we are in if we lose another one today," Barrett said.

"We went into the year with 29 players in our top 30 anyway and we've released some players due to the salary cap restraints that we had.

"We just don't do it for the fun of it, if we haven't let some of these guys go we can't sign a player for next year at all. It has put us in a spot but I would like to see the kid get a go."

Hastings has reportedly fielded interest from Super League clubs and his departure would free up space in Manly's top 30 for Fainu if he signs before June 30.

"If that does eventuate it would open a spot for Manase to come in, if it doesn't I will be sitting here every Monday applying for the same dispensation for him," Barrett said.