St Kilda's youngsters will get their opportunity to show what they’re made of under a new approach outlined on Wednesday by senior coach Ross Lyon.

The club's top pick at last year's AFL National Draft, 200cm ruckman Ben McEvoy is the first beneficiary of the policy after Lyon confirmed the 18-year-old would make his AFL debut in place of the injured Michael Gardiner against Fremantle at Telstra Dome on Friday night.

"We want to really reward the system that's been set up here and we want to reinforce the behaviours that are valued by the team and expected of every team member," Lyon said.

"Those that perform and carry out the behaviours expected of them by their team-mates will stay in the team and those that don't will have an opportunity to go back to Casey and work on that and provide them with solutions to get back in."

Asked what he meant by 'behaviours', Lyon said: "Just what every AFL team would want - to compete, and when you've got to chase, chase, and when you've got to go, go, and be selfless for the team."

"Players, when they're out of form, tend to be inconsistent in those areas."

"It's not about personalities or past performances; it's about what you're putting up week in, week out."

"Obviously push has come to shove and we want to keep integrity in the selection process."

Lyon confirmed that Justin Koschitzke, a late withdrawal from last week's clash with Sydney, would miss again because of his jarred and hyper-extended knee, making the inclusion of McEvoy who, according to the coach, has a good leap and a big engine, timely.

"He's now expected to perform a role for the team in the ruck and up forward," Lyon said of McEvoy.

Lyon warned that not too much should be read into change of direction he outlined.

"There's no admission of anything here bar that we haven't got it quite right at the moment," he said.

"We're not shying away from that, but we're working our hardest and aiming to improve our on-field performance."

"We're really about winning games and developing the team."

Asked whether he believes 'tanking' takes place in the AFL, Lyon replied: "I've never been involved with a team that's tanked."

"I haven't seen AFL games tanked … and that's my perception."

"At the minute my issue is getting St Kilda to play better footy than we're playing."