PORT Adelaide has ruled out defender Ryan Burton ahead of Friday night's semi-final against his former club Hawthorn at Adelaide Oval. 

The 27-year-old failed a fitness test at Alberton on Thursday morning and was ruled out shortly after Power coach Ken Hinkley spoke to the media ahead of the captain's run. 

Burton experienced calf tightness earlier in the week, following last Thursday night's qualifying final loss to Geelong, and hasn't progressed to a point where the club can pick him. 

The South Australian played 11 of the first 12 games of the season before a foot injury and a stint in the SANFL.

Burton was then recalled for the final fortnight of the home and away season and had an important role to play this week with dual All-Australian Dan Houston suspended and Kane Farrell sidelined with a hamstring strain.

Former first-round pick Josh Sinn is favoured to replace Burton and play his first final.

The 21-year-old has only played nine games so far, including four this year, most recently against St Kilda in round 16.

Sinn was an emergency against Geelong, along with ruckman Dante Visentini and Todd Marshall.

Marshall is being considered for a recall in Friday night's knockout final against the in-form Hawks.

Star midfielder Zak Butters was cleared to face Hawthorn earlier in the week and trained freely on Thursday, after being substituted out of the 84-point loss to the Cats last week.