With almost a third of their top-30 roster unavailable, the Sea Eagles blitzed Cronulla to go 18-0 up early and barely let them back into the match.

Without the likes of Tom Trbojevic, Martin Taupau, Curtis Sironen and Joel Thompson, both Daly Cherry-Evans and Addin Fonua-Blake stood up to star in the win.

It was the Sea Eagles' first in the finals since 2013 and books them a date with South Sydney in Friday's sudden-death semi-final at ANZ Stadium.

The loss meanwhile ended Paul Gallen's 348-game NRL career, with the retiring Cronulla captain spending 43 minutes of the game on the sideline.

"I said yesterday it had that script about it (being a backs-to-the-wall win)," Hasler said.

"It's great for this side and a young side to experience something like this tonight. It's a great confidence thing for them.

"For some of them it's their first semi-final. It doesn't come much harder than that baptism of fire against a pretty experienced Sharks side.

"It's a great win, a very proud win in this club's history."

Manly's victory was even more remarkable when considering they laid their platform in the middle against a Sharks pack littered with representative stars.

Manly's three bench forwards - including debutant Haumole Olakau'atu - had played just 10 games between them this year before Saturday night.

Sean Keppie also got through 131 metres starting for the Sea Eagles, just a week after making his NRL debut off the bench against Parramatta.

Fonua-Blake was, meanwhile, immense in Taupau's absence, topping 182 metres.

He scored a crucial try in the 53rd minute to make it 24-10 just when momentum seemed to be going toward Cronulla, pushing his way through three defenders from 20 metres out.

He also pulled off a vital big hit on Braden Hamlin-Uele moments later, forcing an error from the Sharks prop.

Cherry-Evans was typically strong too, setting up two tries in the first half after Apisai Koroisau opened the scoring from dummy-half off the back of a quick Fonua-Blake play the ball.

It came after a chaotic week at Manly, who looked set to lose their home final at Lottoland due to asbestos concerns before 15,495 turned up in support.

"I asked the players, and they said the crowd was massive," Hasler quipped.

Meanwhile, the Sharks' performance summed up their season - one with so much potential but no result.

They missed 11 tackles in the first 15 minutes, while five-eighth Shaun Johnson had a poor first half that included no runs, an error and two kicks that went dead.

He recovered briefly with a big five minutes after half-time when he forced a line drop out and laid on a lofted ball for Aaron Gray to score in the next set.

"There's an old saying in footy, you can't win the game in the first 20 minutes but you can lose it," coach John Morris said.

"That was the case tonight.

"When you're putting pressure on yourself compounding errors ... you're getting zapped and drained."

Bronson Xerri also crossed for one before the break while Josh Morris grabbed a consolation try but it was a case of too little too late for the Sharks.

Australian Associated Press