Widdop pounced from marker when winger Matthew Wright played the ball to no one after cleaning up a kick off his own line.

But Sea Eagles five-eighth Daly Cherry-Evans was restricted from going into dummy half just seconds before Wright played the ball after tangling with Jason Nightingale while trying to get back into position.

Given the incident between Cherry-Evans and Nightingale happened before the ball was played, the Bunker was unable to consider it as a possible reason to disallow the try.

"It's a pretty big one when the dummy half can't get to dummy half and they pick it up and score," Barrett said.

"That's ridiculous, mind boggling, I've never seen it before.

"You can't do it. Jason Nightingale shoved him out of the road. That didn't cost us the game but geez it didn't help.

"We were flat off the kick off and then to cop that on the end of that is very deflating. How they gave that a try is beyond me.

"I'm not making excuses for the rest of our bloody 75 minutes but they don't help, that was under-eights stuff."

"It's a shame that it wasn't involved in the whole process of going to the marker, they neglected that situation in itself but I can't change it," Cherry-Evans said about the incident.

Wright was a late call up into the game for Manly after Akuila Uate pulled out late with a groin injury, believed to be osteitis pubis.

The Widdop try kickstarted a poor afternoon for the Sea Eagles who were looking to build on three straight wins heading into the clash.

They were down 16-0 after 20 minutes and never recovered against a rampant Dragons side which has surged to the top of the ladder after winning four straight games.

Manly had no answers for the dominant St George Illawarra forward pack, which allowed halves Widdop and Josh McCrone to do as they pleased in front of 11,654 dejected fans.

An oblique muscle strain to Tyson Frizell was the only sour note, and the back rower will have scans on the injury within the next two days and remains hopeful of playing in next weekend's blockbuster against North Queensland in Wollongong.

Coach Paul McGregor labelled Saturday's win the best of the year so far for his Dragons, but refused to acknowledge their lofty ladder position meant they were the NRL's best team.

"We go home, we review the game, and get ready for the Cowboys, that's where we sit," McGregor said.

"It's very early in the season and we know we've got to bring it every week to compete at the top. It's great to see where we are but we've got a game next week against a team that's hardened and that's been in the top four for a couple of years now.

"They say we had a big month ahead of us but we're just taking it one week at a time. First one was to come to a ground that hadn't been good to us in the past.

"It was a good opportunity for us to show that our character and resilience is real.

"Manly at different stages came at us especially before half time and after half time but we absorbed that and then we got rewarded."

McCrone was superb for the Dragons setting up four tries with no hint of distraction from the looming shadow of Ben Hunt who will wear his number seven in 2018 when he begins his six-year, $6m contract.

He set up 50 gamer Euan Aitken twice in the opening 20 minutes, putting him through a hole early on before beating Frank Winterstein and spinning it out to his centre who did the rest.

His best came in the dying embers of the game as Sea Eagles fans were streaming from the ground, when he put a kick through to a flying Widdop who managed to ground the ball before it ran dead.

Manly's Jorge Taufua scored a try in each half but otherwise the lacklustre Sea Eagles didn't look like troubling the visitors.

"That performance today was chalk and cheese to the last three weeks, it's a wake up call for everyone," Barrett said.

"We were never in it to be honest. We looked flat, and unenthused.

"Certainly not good enough and not good enough at home, to concede that many points at home is not on.

"We did look tired but that's not an excuse. NRL is an extremely tough competition and if you are off a little bit you get beat and we were off in a big way."