Brisbane's horror start to the AFL season worsened with key defender Chris Johnson facing up to five weeks out with a groin injury.

Johnson was injured during Brisbane's 32-point defeat by Sydney at the Gabba on Sunday - a loss which left the once-mighty Lions rooted to the bottom of the ladder.

It adds another premiership player to the Lions' star-studded injury list, with midfielder Nigel Lappin out for most of the season with a broken ankle and hardman Chris Scott sidelined indefinitely with a hip complaint.

Cold comfort for Johnson is that he dodged a bullet from the AFL match review panel, which ruled he had no case to answer over his report for striking during the Sydney match.

Field umpire Justin Schmitt had reported Johnson for striking Sydney's Tadhg Kennelly.

But the panel threw the case out, along with a report levelled against teammate Jason Akermanis.

The Kangaroos also had bad news, with scans showing tagger Michael Firrito had cracked a bone in his leg.

Firrito injured his fibula during the Roos' fighting 22-point victory over Hawthorn on Sunday and is expected to miss up to two months.

Melbourne could welcome up to five of its injured stars back for its match against Fremantle at the MCG on Saturday.

Skipper David Neitz, forward Brad Miller and defenders Matthew Whelan, Clint Bizzell and Alistair Nicholson all face late week fitness tests.

Teammate Russell Robertson rated Neitz, who has been battling a hip flexor problem, and Whelan, a late withdrawal from Friday night's win over Geelong with a buttock strain, certainties to return this weekend.

"He (Neitz) could have played on Friday night ... but because it was a bit wet, we were able to get away with just having a forward line that we had and giving him an extra week to heal," Robertson said.

"He's going to be cherry ripe this weekend."

St Kilda ruck-forward Justin Koschitzke remains in hospital and underwent more scans on Monday on his fractured skull, which is likely to sideline him for at least six weeks.

Koschitzke was felled in a sickening clash with Western Bulldogs midfielder Daniel Giansiracusa during the Saints' victory on Saturday.

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