St George Illawarra's Jack de Belin has taken aim at his NRL team for playing selfish and not giving their all.

And he admits his form has stagnated as the Dragons battle a slump threatening their spot in the top eight.

The Dragons sit eighth on the ladder and play third-placed Manly at WIN Stadium on Sunday, with a loss possibly relegating them to ninth if Penrith score a big win over Gold Coast.

"We've got away from our team-first actions and are probably playing a little bit individualised at the moment," de Belin told reporters on Tuesday.

READ MORE:

* NSW Blues' pub session probed

* Johnson out for 6-8 weeks

* Thaiday to depart Broncos in 2018

"Like your little effort things ... for example, kick-chase, kick-pressure, working hard on your insides, supporting your mate.

"When we're playing well, (we're) doing those little things and not just worry about our carries.

"We probably haven't been doing it to 100 per cent of our effort. If you're only doing them at 50 per cent, you're not doing them well."

The star lock was close to making his State of Origin debut last week as NSW 18th man, with injury clouds hovering over Blues forwards Tyson Frizell and Boyd Cordner.

De Belin's numbers have been solid for the Dragons in 2017, improving his offensive output from last season but averaging seven fewer tackles per game.

The 26-year-old is unsatisfied with his recent performances as the Dragons reel from losing four games from five starts, including Friday's golden-point loss to Canberra.

"It's (form) been pretty steady. If anything, I'm probably a little bit disappointed I haven't really continually built on it," de Belin said.

"I've just kind of plateaued."

De Belin has also spoken about the frustration around being part of a NSW squad with his sights set on playing in last week's decider against Queensland but he wasn't required.

Teammate Frizell and Blues captain Cordner both got up for the game - unexpectedly for de Belin.

"I didn't want to get my hopes up but seeing Boyd earlier in the week, I didn't think he was going to be very good," he said.

"Even Tyson, he's been battling injuries for a while now. I thought my opportunity would come there but it didn't and it is pretty disappointing."