ANYONE dubbed 'Lethal' is not easily frightened.

But Brisbane Lions coach Leigh Matthews described the sight of key forward Jonathan Brown limping off the field against North Melbourne on Saturday night as "pretty scary".

However, Matthews said he was optimistic about his prized co-captain's chances of overcoming a left knee injury and running out against Fremantle at the Gabba on Sunday.

The Lions held their breath in the third term against North Melbourne when Brown hyper-extended a knee for the second time this season, only to return soon after and finish with six goals in the 31-point win.

Brown was still expected to be racing the clock to be fit for this weekend - but Matthews seemed more concerned about Ash McGrath, describing him as "most unlikely".

McGrath, Josh Drummond and Jason Roe all suffered hamstring injuries against the Kangaroos.

"I am optimistic he will play this week," Matthews said of Brown.

He didn't share that view when he first saw the reigning Coleman Medallist grimace in pain and put in the care of club doctors last Saturday night.

"I asked the medical people again about it this morning. It looks like you are crippled and then 10 minutes later it eased up again," Matthews said of Brown's injury.

"At the time it was pretty scary because it does look severe."

The Lions (6-4 record) have snuck up to seventh place, just one win outside the top four, with three straight wins but Matthews dismissed the notion that the Lions were "flying under the radar".

Indeed he did his best to talk up the Lions, describing their weekend form as exceptional.

Only goalkicking inaccuracy blighted their performance, with Brown one of the biggest culprits kicking 6.7 on the night.

"That's as good as we have played. Except the conversion part, it was a bit sloppy," Matthews said.

"That kept the scoreboard close, but it was an exceptional win against competitive opposition.

"It is encouraging that we have been able to win three games convincingly."

The Lions are in the box seat to stitch up four straight wins against a Dockers side that has never won in Queensland.

Fremantle is vulnerable after letting a three-quarter time lead slip away for the fifth consecutive week.

"They have this strange, quirky thing where they have bad last quarters," Matthews said.

"We haven't gone great in last quarters (winning only two in 10 games in 2008) but when we had to be okay we were which was last Saturday.

"They (Fremantle) have been in most games but haven't squeaked out the win - they haven't been playing horribly."