A fuming Brad Arthur says his middle forwards simply "didn't want to tackle" as Manly rattled up a 36-24 win that continues Parramatta's inconsistent 2019 campaign.

Two late tries flattered the Eels as they well and truly came off second best against their old rivals, a promising three-game winning run ended in the process.

Sea Eagles star Tom Trbojevic had a field day through Parramatta's middle off the back of endless quick play-the-balls, Arthur giving a blunt assessment of his team's defence afterwards.

"It was a step backwards," Arthur said of the demoralising loss.

"I'm not sure why we didn't have any intent from the start.

"We got run over through the middle. Everyone could see that, but it was why? Why did we have that attitude?

"We talked about our defence needing to improve all week.

"It might have been 55-60 minutes before we got off the line and started to commit to our contact.

"It's got nothing to do with ability otherwise they wouldn't be in the team. They know how to tackle they just didn't want to tackle early."

The Eels still reside in sixth place after the loss but another defeat to the Warriors next Saturday could mean they drop out of the top eight for the first time this season.

Star winger Blake Ferguson remains in hospital with a leg infection and according to Arthur is unlikely to be fit for the clash.

Mid-season recruit Waqa Blake is however expected to be available for his first game since moving from Penrith.

But with Manly racing in four tries in 11 minutes before half-time and Tom Trbojevic "playing touch footy" through the middle third of the field, Arthur was more focused on rediscovering much-needed defensive resolve when his team is under pressure.

"I don't want sit here and say it's that easy, we've just got to defend one set," he said.

"But once we get put under the pump we need to find the effort and energy to defend a set, make sure they have to kick from inside their half and then get the ball back and roll our sleeves up.

"The last couple of weeks we've rolled our sleeves up. We didn't want to today."