Manly coach Des Hasler has admitted he's worried about his depleted team's inconsistency and suggested he would "keep trying things" at the selection table.

Without injured stars Tom Trbojevic and Dylan Walker and the suspended Addin Fonua-Blake, the Sea Eagles slumped to a 34-4 loss to the Dragons at Netstrata Jubilee Oval on Sunday.

Trbojevic and Walker are still about a month away at least from returning but the Sea Eagles can't afford to wait that long to rediscover their mojo as they sit in 10th place.

"It's probably the week-in, week-out performance that I'm concerned about," Hasler said.

Manly dug deep to beat Canberra when Trbojevic and Walker limped off in round six, then were flogged by Cronulla the next round. 

Match Highlights: Dragons v Sea Eagles

They produced another gritty effort against Newcastle last week and Hasler was disappointed they again failed to back it up.

He thought Manly began well in attack against St George Illawarra as they built pressure and scored the first try but there were few other positives in a display that featured 13 errors.

"We're just not competing for long enough, so it's not going to change and we need to fix it," Hasler said.

"No doubt we'll lick our wounds and we'll go back this Saturday night against a red-hot Parra side.

"We've got to have a red-hot dig. They're trying."

Hasler brought Cade Cust in as starting five-eighth, with Lachlan Croker moving to the bench, while Brendan Elliot played fullback and Reuben Garrick switched to the wing. Tevita Funa dropped out.

Cherry-Evans goes short to Thompson

"Brendan with his work at one - he probably knows his way around it a little bit better," Hasler said in explaining the changes.

"And I thought Cade Cust just gives us that bit of directness at half."

But he conceded the Sea Eagles are yet to find their best available spine and foreshadowed more tinkering.

Hasler said the attention surrounding Fonua-Blake's two-match suspension for an offensive outburst last weekend hadn't distracted the team.

Captain and halfback Daly Cherry-Evans endured a tough night but Hasler has no doubt the Queensland Origin star will rebound.

"It's not that he's trying too hard, sometimes you just have those games. It's very rare," Hasler said.

"He'll fix that, he's a real professional in the way he goes about it. He'll find a preparation this week, he'll come back."