Manly are just one step away from a shot at premiership redemption with a 38-6 qualifying final victory that killed off St George Illawarra's NRL season.

The seven tries to one win at Brookvale Oval secured Manly a week off and preliminary final in Sydney for a chance to contest the 2008 grand final.

But it was far from Manly's best performance with the Sea Eagles riding plenty of luck, incurring injuries to centre Steven Bell (calf) and prop Josh Perry (knee) and producing a couple of suspect tackles that could come under match review scrutiny on Monday.

Manly led 20-6 at halftime after weathering an early barrage before storming home in the second half to the delight of 19,227 fans.

The match was in the balance at 8-6 prior to halftime before two tries to Michael Robertson and Anthony Watmough in the five minutes before the break gave complete control to Manly.

The Sea Eagles never let their ascendancy slip in the second half with three tries in nine minutes - to Brett Stewart (58th minute), Heath L'Estrange (63rd) and David Williams (67th) - securing the big win.

Stewart had claims at a double as he and L'Estrange both got hands to the ball in the 63rd minute and even though the fullback won an on-field game of paper-rock-scissors the try was awarded to his hooker.

Prop Josh Perry was one of Manly's best and capped his great night with a try in the 77th minute simply by backing up his teammates.

But less than 60 seconds later he was chaired off the field with a suspected knee injury that could seriously derail Manly's premiership charge.

It was a sour way to end a night of celebration as departing veteran Steve Menzies scored the first try and then badly shanked the final conversion attempt in his final game at Brooky.

The 347-game veteran opened the scoring in the 12th minute when he charged down Ben Rogers' audacious chip on the halfway line.

He toed the ball ahead but almost blew his own try when he tripped and head butted the ball before grounding it.

Manly led 8-0 while the Dragons for all their dominance simply could not break the defensive line.

When they finally did in the 25th minute, with Josh Morris racing over, it was unluckily denied by the video referees who ruled an obstruction by Lagi Setu against Matt Orford.

But the Dragons got retribution two minutes later with Mark Gasnier crossing in the corner despite an apparent forward pass by Setu in the lead up to reduce the deficit to 8-6.

That was the last of the Dragons' real attacking chances as their season of promise faded into a disappointing farewell for departing stars Gasnier, Jason Ryles and coach Nathan Brown.

Manly captain Matt Orford praised his side's defensive effort but said the job was nowhere near complete, with the Sea Eagles desperate to avenge their 2007 grand final defeat to Melbourne.

"It's just a long way to go, we cannot get carried away yet," said Orford.

"Things are building quietly and we need to make sure we are right for the game the following week.

"We are in a good position now, we just have to make the most of it."

Brown lamented wasted opportunities in the first half as his long career at the club came to a disappointing end.

"I have been here 17 years now and it's been a great journey but unfortunately we have never got the end result we all would have liked," said Brown.

"Not everyone gets the fairytale finish. We got the not-so-good finish. But life goes on."

Gasnier, who departs to begin his career in French rugby union, said he was shattered with the result and added it was unlikely he would ever play league again.

"Probably not, I think this is it," he said.

"To be honest I feel crap, but it's more for the loss not because I am going."

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