The erratic Cronulla could finish the weekend as high as third - but conversely be as low as sixth - depending on the result of their clash with the third-placed Roosters at Southern Cross Group Stadium on Saturday night.

It's a symptom of a finals logjam, which only has minor premiers Melbourne guaranteed of their finishing position over the final fortnight of the regular season.

And a loss to the Roosters - who they've beaten in their past six clashes - in a high stakes top-four shootout would almost certainly condemn the Sharks to trying to lift back-to-back trophies from outside the top four and re-write even more rugby league history.

But try telling Flanagan the Sharks aren't capable of winning a competition from there, particularly when it comes to last year's grand final foes Melbourne who have been the benchmark in 2017.

"I believe we can beat them," Flanagan said. "I'm not quite sure about the other teams. We definitely know we can and we definitely believe we can. We'd love to get a crack at them. If you can guarantee me a grand final position and it was against the Storm we'd be happy.

"We want to finish in the top four. Teams can put a good month together and a side is going to come out of that bottom half of the draw eventually [to win a competition], but we'd like to finish in the top four and if you win that first semi-final you put yourself in a great position to play in a grand final."

But first are the Roosters, who can seal a top-four finish and two bites of the finals cherry with a win over a team they never seem able to beat.

The Sharks battered the tricolours at Central Coast Stadium earlier in the season and Flanagan is again laying down the law to his big men Andrew Fifita, Matt Prior and Paul Gallen before they run out at an anticipated sellout in the Shire.

"They've got [Jared Waerea] Hargreaves, [Dylan] Napa and some quality forwards and we like to test ourselves against those types of players," Flanagan said. "It's hard to put your finger on why [the ledger] is between the two clubs.

"If we start well through Matty Prior, Andrew and Gal ... they're the ones that are going to decide the result for me. If they get over their opposition we win."

Roosters coach Trent Robinson is relishing the chance for his side to resurrect its record against the Sharks and confirm a top-four spot.

"We've worked ourselves into this competition and are in a good position, but I think we've got to prove that [on Saturday] night against a really quality opponent," Robinson said.