They've been kings of the close-down for the past four NRL seasons, but Melbourne prop Brett White admits stopping Parramatta's second-phase football will be their biggest challenge on Sunday.

Melbourne's defence has been the foundation from which they've built their success, but White said the Storm hadn't encountered anything quite like the Eels.

Parramatta threw a season-record 41 offloads in their preliminary final win over the Bulldogs last week and it is their ability and constant desire to keep the ball alive that has Melbourne wary.

"I guess they're a lot different to us, we're quite structured," said White.

"Anything can happen (with them). It's very hard to prepare for that because you don't know what you're preparing for.

"Jarryd Hayne can do anything and that's the difficult part about it, just trying to make sure we don't leave too many gaps around."

The Storm held an open training session for fans at their Carlton headquarters on Wednesday with close to 1000 supporters there to see them off to Sydney.

But for an AFL-town, most would have been scratching their heads at the sight of two footballs being used in Melbourne's defensive drills.

The idea is that while the players retreat, thinking the play has been shut down and tackle complete, a trainer would suddenly throw the second ball into play forcing the Storm to quickly re-set their defensive line.

It is not an uncommon training drill for rugby league teams and it's the closest you can get to simulating the electric Eels and their brilliant match-winner Jarryd Hayne.

"It's the challenge that we face, we're fully aware of that situation," said White.

"We have to make sure we get it right by working hard in the middle and trying to fill up all the gaps.

"It's a big thing trying to stop, it's like a leaking tap or something. You just have to keep plugging up the holes and hopefully (Hayne) doesn't get through.

"(But) it's something we've had all year is confidence in each other. It goes a long way, especially in games like this when it's such a big importance."

Meanwhile White said he believes the club's grand final experience of having been in the past three successive deciders would be an advantage over the Eels.

Only three Parramatta players have played on the biggest day of the year while for Melbourne, White is one of six players to have been there for the past four straight seasons.

"It's always hard going into games like that unknown," he said.

"I think going out there and being there before and being able to relax and enjoy it more, we know what's got to be done."

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