THE BRISBANE Lions have been dealt a blow with important midfielder Allen Christensen breaking his collarbone at training.

AFL.com.au understands the premiership Geelong forward, who crossed to the club at the end of the 2014 season, is expected to miss at least six-to-eight weeks after suffering the fracture.

It is a setback for the Lions and Christensen, who has had a strong pre-season as he looks to get back to his best after injury restricted him to just 11 games last season. 

The club confirmed Christensen's injury late on Saturday afternoon, saying the extent of his layoff would be known after scans on Monday. 

The Lions look set to be without Christensen for the start of the home and away season next month but will be keen to have him available as soon as possible as they enter a new era under coach Chris Fagan. 

The 25-year-old has played 98 games since making his AFL debut for the Cats in 2011, when he went on to play a pivotal role in the club's Grand Final win over Collingwood that season.

He departed Geelong just three years later and played 22 games in his debut season for the Lions in 2015, after joining the club alongside star recruit Dayne Beams.

Christensen did not play in the Lions' opening JLT Community Series clash last week against Gold Coast, which the Lions lost by four goals.

The Lions are expected to again field a young side throughout 2017 as they aim to push themselves up the ladder after finishing second bottom last season.