From contenders to pretenders in the space of two weeks, the Sea Eagles' season is threatening to blow up in their faces.

It was only a fortnight ago on a sunny afternoon at Brookvale that Barrett's team romped home to claim the prized scalp of the Sydney Roosters, re-energising their bid for a top-four berth.

Suddenly, the outlook is nowhere near as bright on the northern beaches. Consecutive defeats to lowly Wests Tigers and now Canterbury have left them clinging to eight spot with two rounds remaining and a seemingly inevitable return to the semi-finals after a three-year hiatus is no sure thing.

Manly captain Daly Cherry-Evans had been ill in the lead-up to Sunday's match and didn't get any relief in a 14-point loss that featured a pair of tries each to Bulldogs wingers Marcelo Montoya and Brett Morris.

Before a meagre crowd of 8912 at a cavernous ANZ Stadium the Sea Eagles' wings were clipped again by an unlikely conqueror.

"We're in a hole, to be fair, and down on confidence and probably lacking a fair bit of belief," Barrett said. "I thought Canterbury played with more intent than us today and it reflected our scoreline.

"How does it happen? If everyone had the answer to that you'd be a very successful coach and it's something I've got to work out and work out quite quickly, as have the players. Our performance was probably a little bit like the atmosphere out there ... very lacklustre considering what we had to play for."

This time a month ago, Manly were third but have since lost four of five matches to slip down the ladder. One issue Barrett must address urgently if they are to figure next month is defence. They have leaked 170 points in those handful of games and their vulnerabilities were again exploited on Sunday.

Worryingly, it's between the ears that they seem to have a problem.

"The look in everyone's eyes is just not there at the moment," said five-eighth Blake Green. "We went from a team that were gritty and tough and resilient and worked really hard and those things that we got a lot of wins from just haven't been there the last couple of weeks."

Manly were "shell-shocked" trailing 12-10 at half-time, Barrett said, and never recovered in a six-tries-to-three defeat. They must pick themselves up for next weekend's visit across the Tasman to play New Zealand Warriors before a potentially season-deciding clash with Penrith in the last round.

"You can't go from being the side we were for the 21 weeks and being as high as third to playing like we are at the moment," Barrett said. "I just think the intent in everything we do is down at the moment."

After being run down by the Tigers the previous Sunday any thought of Manly getting an easy ride against another of the competition's bottom four teams was quickly dispelled. The Bulldogs, having switched Moses Mbye to halfback and promoted Michael Lichaa to hooker, took advantage of penalties to cross the line twice down the right corridor in the first 16 minutes. Rookie Montoya finished off both plays but had some smart passing from Will Hopoate to thank.

While Hopoate has failed to score a try himself in 16 matches this season these two were his in all but name as he picked apart his former team's defensive weakness on their left side.

The Sea Eagles split Montoya's double by keeping the ball alive, the hot potato finished off by Jake Trbojevic and then from a scrum as Tom Trbojevic sent centre Brian Kelly over. Unperturbed, Hasler's side reclaimed the lead just before the break via Brett Morris before Hopoate once more became provider to stretch their advantage, this time for Brenko Lee as Kelly and Mat Wright were again left stranded.

Cherry-Evans' unhappy day was then summed up as he got an ugly bounce from a Matt Frawley kick - Josh Morris seizing on the fumble to score - and was later beaten by the same man for speed. For the second time Morris's brother Brett was the beneficiary of his handiwork, the winger's second try sealing a victory a long time in the waiting and one that will lift spirits.

Cherry-Evans and the Sea Eagles, by contrast, have some soul searching ahead.

"We've got some things to sort out in the next fortnight before we go into a semi-final," said Barrett, "because we won't last long."