COLLINGWOOD defender Harry O'Brien believes Nick Maxwell is the Magpies' most important player and says they will be a better outfit should he return from a broken thumb this week against West Coast.

Maxwell has put his hand up for selection just over three weeks after having his right thumb pinned and plated after he sustained the break against St Kilda in round 21.

O'Brien said the expected return of the captain would make a big difference to the side, and would bring a new level of voice and direction to not only the backline but the entire team.

"I must say I'm biased because I'm a defender but it's like having a coach on the field," he said on Tuesday.

"When Mick [Malthouse] delivers a message it's so spot on the mark, and he delivers something to you at quarter time and you can adjust but having Nick Maxwell out there, it's as though you have a coach out there.

"His knowledge of the game plan and the way the coaching panel want us to play is by far the best out of any player in the team.

"Contrary to a lot of external opinions and the question of whether he's in our best 22, for me, playing alongside him, he's our most important player."

The Magpies have endured persistent changes to the back six that led the team through the finals series last year.

Maxwell has missed the past three games, Nathan Brown has been out all season with a knee injury, Alan Toovey was absent from rounds 18 to 21 because of a broken finger and Heath Shaw has been suspended since round 17 after betting on the game.

Tyson Goldsack is another who has only managed to recently string games together, playing from round 18 onwards.

Chris Tarrant has restored some balance with 20 games while O'Brien has played all bar round 20 and Leon Davis has been reinvented as a running defender but missed last week with hamstring tightness.

O'Brien said the changes to the backline across the season had been a challenge, but had ultimately improved the team's depth with finals in mind.

"I think if you go back through history, the premiership teams, they've had a really settled defence," he said.

"It has been a challenge with young guys like Ben Sinclair, Tom Young and Luke Rounds who have very limited experience but I think it's served us well.

"We know they can come back and play a role if anyone does fall over during the course of the finals, and we've got no hesitation of bringing them in to play their role."

Davis, Maxwell and Shaw are all potential inclusions this week for the Pies' qualifying final, although Malthouse warned on Monday the selection committee could get nervous about bringing in three players - particularly with two that have missed a fair amount of football - together.

O'Brien said it would be handy to have all three, especially given Davis' emergence as "the best run and carry player in our team if not the competition" in the absence of Shaw.

"Just to have that experience … especially Heath, as annoying as he is, he's actually a very a good leader down there," he said.

"'Maxy' is such an inspiration on and off the field and to come back from a broken thumb, and a lot of people wrote him off but I always knew he's be back for this final.

"I've lived with him and seen the way he goes about it and it's just going to be very important for me as well to have those leaders down there."

O'Brien also said a focus for the backline this week was to attempt to exploit the Eagles' big forwards with creative run from defence.

"Certainly a theme for us this week is to be bold and to play a courageous sort of football … not so much courageous in terms of running back with the flight but to have the courage to take risks and really back our running abilities down back," he said.

Meanwhile, midfielder Ben Johnson has put his hand up for selection despite aggravating the sore knee he has carried for a number of weeks on Friday night against Geelong.

Johnson said he was fine to face the Eagles and expected to be fit for the rest of the finals despite the nerve-related pain.

"I'm feeling good. I was a bit sore and there was a pinch of the nerve in the knee," he told afl.com.au on Tuesday.

"It's just when I kick the knee cap rubs along some nerves so it can be painful when I kick.

"Structurally, the knee is amazing so it's just a little painful but it will go away. I'm not too sure how it happened. It's wear and tear and I've had it for a few weeks.

"It's nothing serious at all so I'll be fine. I'll be playing."

Jennifer Witham covers Collingwood news for the AFL Website. Follow her on Twitter @AFL_JenWitham.