MATURE-aged rookie Zac O'Brien has been upgraded to the Brisbane Lions' senior list to cover injured skipper Tom Rockliff.

Rockliff was subbed out of Saturday night's loss to Collingwood with broken ribs and a punctured lung.

He spent two nights in hospital and will miss up to six weeks of football.

O'Brien was elevated to the club's main squad twice last year, firstly for ruckman Matthew Leuenberger and then for Daniel Rich.

Lions coach Justin Leppitsch said that after a strong pre-season the 24-year-old would have been in line to play in round one had he been available.

"He has been unlucky, being a rookie probably kept him out of the side while we went with players we knew we could use," Leppitsch told News Limited.

"But he is available now and is a strong chance to play this week."

Leppitsch said he hadn't decided who would captain the side in Rockliff's absence, but vice-captains Daniel Rich and Dayne Zorko are favourites to share or alternate in the role.