Inspirational Brisbane captain Jonathan Brown has had his face fractured in a sickening collision for the second time this AFL season.

Brown, who missed six games after having his face badly injured in a collision with Fremantle defender Luke McPharlin in the opening round, was this time knocked out cold in a four-man collision late in the Lions' loss to Geelong on Sunday.

Initial x-rays cleared Brown but further scans on Sunday night found the three-time premiership star had sustained a number of small facial fractures.

Brown will have his second bout of surgery for the season on Monday.

While the Lions were unsure how long the latest injury would sideline their skipper, if the recovery time is similar to his previous stint, it will most likely end his season, which would be another huge blow in what has been a difficult year for Brisbane.

Even before the full extent of the injury was known, coach Michael Voss said that while Brown's courage was inspirational, the universally respected 195cm, 104kg forward might have to review his fearless approach to physical danger.

"Someone has to tell him he is not 21 any more," Voss said of the 29-year-old.

"(But) it's hard to tell someone 'instead of going at 120 per cent, go at 110'.

Yet despite that warning, Voss could not his admiration for his former premiership teammate.

"To be led by that guy, no wonder the guys want to come to the well - that's unbelievably courageous," he said.

"He's always maintained that character about him and that is why he leads from the front.

"And we have some others who are joining in."

The Gabba crowd hushed when Brown was knocked out.

His head slammed the turf and medical staff worked on him for minutes before he was taken off on a medicab.

Scores were level at 77-all at the time, with the Lions initially digging in to reach the final break up three points, before Geelong stepped up in the last quarter.

But Voss still found a positive in that Brown did not score a goal for the day, yet the Lions were able to push the second-placed Cats until deep in the match.

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