Christian Petracca starred as the Demons overcame a wasteful start to beat the Cats 12.13 (85) to 9.6 (60) in front of 33,728 fans at the MCG and go 4-0 for the first time since 1994.

May was substituted off in the second quarter for Tom Sparrow after he was left bleeding profusely above his right eye when Geelong's Tom Hawkins threw his elbow back in a bid to break a tackle.

The defender was later taken to hospital, with concerns over a potential eye socket injury - while coach Simon Goodwin was uncertain whether May had also suffered a concussion.

"He's gone to hospital, getting some stuff around his eye checked out - so we're not sure what that looks like yet, we'll wait and see," Goodwin said.

"But clearly he's going to miss a few weeks - so that's disappointing but it gives opportunity."

In May's absence, Jake Lever marshalled Melbourne's defence with aplomb while Adam Tomlinson did a solid job on Hawkins.

Goodwin said Harry Petty was a potential option to replace May but forwards Ben Brown and Sam Weideman are still "a few weeks away" after returning from injury via the VFL.

Mark O'Connor tagged Clayton Oliver, but it was Petracca who proved the main event, dominating with 36 disposals, nine clearances and two goals.

"To have the impact he had today, we're really happy for him because that's been coming for a few weeks," Goodwin said.

Bayley Fritsch (four goals) was excellent for the Demons, while Cats skipper Joel Selwood (30 disposals) did a mountain of work at the stoppages.

After the Demons were wasteful in the first term, Fritsch booted three goals in the second quarter and Petracca snapped his second with the last kick of the first half to nudge Melbourne's lead out to 23 points.

The Demons got out to a five-goal lead in the third term before the Cats fought back, with Isaac Smith's second goal cutting the deficit to 12 points at the final change.

But Melbourne held firm to maintain their unbeaten start and ensure the Cats slipped to 2-2.

"We're not playing the footy that we'd like to," Cats coach Chris Scott said.

"I thought we were well and truly in the game at three-quarter time (and) arguably had our chances but they were in control all day."

Geelong lost Brandan Parfitt (hip) before the game, with Quinton Narkle a late inclusion, but Scott expected the midfielder to be fit to face North Melbourne while Mark Blicavs suffered a corked knee late.

Meanwhile, Goodwin said he'd been unaware Melbourne president Glen Bartlett had stepped down until he received a club email on Saturday night - but lauded his "eight years of great service" in the role.

Australian Associated Press