SOME doubt surrounds Michael Hibberd's availability for Friday night’s semi-final against Hawthorn after the star defender left training early on Tuesday. 

Hibberd completed the warm up with teammates but appeared to feel discomfort in his right knee. 

The defender took his boots off and changed into runners to join the rehab group training away from the main team. 

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Hibberd completed a number of laps as he looked test things out, before a conversation with the club's fitness staff led to him leaving the track early. 

The Demons played down any concerns and said he was having a light session and training indoors as part of his program. 

Christian Petracca had his right knee taped up by the trainers, but it was soon apparent that he had only suffered a cut that needed to be dealt with. 

Defenders Jayden Hunt and Joel Smith were part of the club's match simulation session with the senior team as they look to push their case for selection.