PORT Adelaide will head into Friday night's preliminary final unchanged as coach Ken Hinkley backs Todd Marshall to make an impact after a quiet run of form.

The Power will face Richmond at Adelaide Oval in a bid to win through to next week's Grand Final and will head in unchanged from their qualifying final win over Geelong.

Todd Marshall (shoulder) and Xavier Duursma (concussion) have been cleared to take on the Tigers, who are weighing up bringing in Mabior Chol for ruck back-up. 

But Hinkley said on Thursday his best 22 is set, confirming Marshall as a starter. 

"We'll be no change. He'll be fine. Xavier was the other who came out of our last game who might have some doubt over but both boys trained well this week and are ready to go," Hinkley said. 

Marshall has kicked only three goals from his past seven matches and averaged fewer than two marks in that period but Hinkley said the 22-year-old's impact lay in different areas. 

"Output from numbers only is one thing but you've got to value the whole thing and for us we value what Todd brings amazingly to our team. We've got a great record with Todd in the side," he said. 

"There's so many times that you just need to be in the right spot and it helps other people. 

"The stats don't purely tell you that – they don't tell you exactly what's going on in the game style we're trying to achieve and Todd's an incredibly important part of that game style."

Hinkley said the Power was proud of its performances so far to reach its first preliminary final since 2014, but said the group was excited to take another step after finishing the home and away season on top of the ladder.

The Power's healthy list means veteran Justin Westhoff, who will retire at the end of the season, has missed selection in the do-or-die final. But Hinkley said sentiment had to be put aside at this stage of the season. 

"It's hard to leave him out, there's no doubt about that. With a servant like Justin has been to our football club, it is really difficult not to have him in the team," he said.

"But we also have to respect that we've got to pick the team that gives us the best chance and we think the 22 that we've picked give us the best chance.

"'Westy' certainly understands that, as much as he's really, really keen to be able to be out there, he knows exactly where he's sitting."