Melbourne's brutal wet weather towelling of top four rivals the Sydney Roosters has come at a cost, with Test backrower Ryan Hoffman likely to be sidelined until at least the NRL finals.

In a 30-6 win at Olympic Park which demonstrated Melbourne's credentials for back-to-back premierships, Hoffman was carried off midway through the first half after injuring his ankle.

Hoffman's leg was trapped awkwardly as he tackled a Roosters player, and he also received a cut to his head.

After struggling to walk, Hoffman was chaired off the field by two trainers and didn't return to the field, with scans on Saturday to determine his fate.

Storm coach Craig Bellamy suggested Hoffman was likely to be sidelined at least until the finals.

"It's his ankle that's the problem so it's going to be a couple of weeks at least, if not worse," Bellamy said.

"That's not good news for us. He'll have a scan tomorrow and see how he goes."

Hoffman's injury was the only dampener on an awesome Storm performance, in which Melbourne sent a statement of intent to the rest of the competition by bouncing their second top four rival in the space of a week.

The premiers ran a first half steamroller over the Roosters, then extended their advantage in trying second half conditions as heavy rain swept Olympic Park.

Storm winger Anthony Quinn, who this week signed a new four-year contract with the club, scored two first half tries as his side raced to a 20-0 lead at the break.

Skipper Cameron Smith, halfback Cooper Cronk and fullback Billy Slater added the other tries - Cronk and Slater touching down inside the last five minutes after Roosters centre Mitchell Aubusson had grabbed a consolation try in the 73rd minute.

The win lifted the Storm two points clear at the top of the NRL ladder - perhaps only temporarily as Cronulla could join them tomorrow if they beat the New Zealand Warriors away.

But the victory - just seven days after the Storm beat Manly to join them and Cronulla on top of the ladder - lifts them back into serious contention for their third successive minor premiership.

The manner and authority of the win suggests it will take an off-day or arming their rivals with guns to derail Melbourne over the next three weeks.

Roosters coach Brad Fittler described Melbourne as "a class above" his side on the night - as they continually pressured his side into error especially in a virtually error-free first 40 minutes.

"We competed pretty well but their execution in these conditions under pressure was excellent - they do it so well," Fittler said.

Melbourne coach Bellamy, known as a hard taskmaster, paid tribute to his side's awesome first half effort.

"It was a good performance, especially the first half. It's hard to be critical of too much we did," Bellamy said.

Roosters hooker James Aubusson was also a casualty of a tough first half after sustaining two heavy head knocks in the space of five minutes.

First he was accidentally kneed in the head by Slater as he attempted a tackle, then was turned into a doormat by man mountain Israel Folau to leave him completely dazed and confused.

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