St Kilda coach Ross Lyon says letters from concerned supporters have helped shape his view that he needs to introduce new blood into the AFL team.

Ruckman Ben McEvoy will make his debut against Fremantle on Friday night, with Lyon saying there could also be another one or two young players brought into the side.

The coach said with the Saints losing four of their past five games, it was time to ignore reputations and put all players on notice that they would be dropped if they did not follow team "values".

"Reputations really count for nothing, particularly when you're 5-7 and you've won one out of five," Lyon said.

"We'll all be judged, it's not about personalities and past performance, it's about what you're putting up week in, week out."

Lyon said he had taken note of complaints from supporters who believed some players were persevered with despite their performances not warranting continued selection.

"There's no doubt you get letters from supporters and probably (they are saying) `a few of the players have been given a lot of opportunities'," he said.

"'We see the same broken tackles, we see the same missed shots at goal and we implore you to give youth an opportunity'.

"We're all aware of that and the reality is through injury and necessity and opportunity it starts this week with Ben McEvoy and there's likely to be maybe another one or two."

Asked if any letters had particularly stuck in his mind, Lyon said there was one from a Melbourne lawyer urging change.

"It was basically that message: `The time's now and we implore you for the club and its future to make some hard decisions.'

"They ring true, those messages, they're a bit like some media articles, when they're factual and they've got some good research in them, you can take a bit out of them."

Lyon said the move towards youth was not a signal that the Saints had given up on making the finals and were looking towards future seasons.

"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."

He said they took a similar approach last season when they were 4-7 at the halfway point and ended up notching seven wins and a draw in the second half of the season to narrowly miss the finals.

"There's some teams sitting in the competition that can clearly plan for finals," he said.

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

Key forward Justin Koschitzke has been ruled out with the knee injury that kept him out of last weekend's loss to Sydney.

But Lyon said veteran Robert Harvey was likely to play, despite having experienced calf soreness.

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