Champion Carlton forward Marc Maclure, now a respected commentator, says struggling Saint Justin Koschitzke is "finished" and his poor form has become "horrifying to watch".

Koschitzke's worrying performance against Collingwood last weekend - the latest in a long list this season - has again sparked debate over his value to a side firmly in the premiership mix.

He had only eight touches in the MCG blockbuster, kicking just the one goal, although several teammates were also well beaten in the stunning 48-point loss.

While coach Ross Lyon has staunchly defended the forward-ruckman at every opportunity this season, believing he provides crucial team balance, Maclure has now questioned that.

Koschitzke last year kicked a career-high 48 goals, although only three in the finals, and took 45 contested marks while predominantly used at full-forward.

This year, despite the long absence of skipper Nick Riewoldt, leaving Koschitzke as the primary marking target, he has just 12 goals and appears to have lost the ability to take a contested mark.

He averages 4.5 marks per game this season, down from 6.7 last year.

"I think he (Koschitzke) is finished. I just don't know how he fits in anymore," Maclure, also a former Saints assistant coach, told BackPageLead.

"I am really worried about him. He can't find the ball, he gets pushed out of the way too easy, he just doesn't look right to me.

"Forward players now need to be quick, real quick, and agile, and not robotic in a sense. He is just a straight-line runner. As soon as he touches it, he can't catch it.

"I said something after the game - you can make all the excuses, talk about all of the things he is doing with the team-balance thing, but he is not doing that anymore, can't possibly be playing to the team rules.

"I think it's getting to the stage where his head actually goes down all the time. He does something wrong and goes: ‘Shit, I've done that again. I just keep doing the wrong things all the time'.

"It's sad."

Maclure, a former Carlton captain and three-time premiership player, said he hadn't witnessed a decline as rapid as this in more than 35 years in the VFL-AFL.

"Not like this and not in the dramatic fashion it's happened. He had that knock to the head (with Daniel Giansiracusa in 2006)," he said.

"He has had some horrific problems. It's actually now horrible to watch, even for his family and him. There are no winners here."

Former St Kilda coach Grant Thomas and Essendon great Matthew Lloyd have repeatedly said through the season that Koschitzke, the No.2 pick in the 2000 draft, would be best utilised as a permanent ruckman.

Thomas also said Koschitzke, 27, hadn't been used properly as a forward in Riewoldt's absence, trying to emulate his captain on the lead rather than playing to his strength as a long, contested-mark target.

In Lyon's favour, he has at least ensured Koschitzke has been fit, managing 19, 22 and 23 games between 2007-09.

After 20 games in his debut season of 2001, repeated injuries, often blamed on pushing him into the ruck too early, restricted him to 4, 17, 17, 13 and 7 matches before Thomas was sacked after the 2006 season.

Former St Kilda coach Stan Alves says Koschitzke may be suffering from "paralysis by analysis" and simply needs to get to more contests.

"It sounds silly but at this point of time he just has to be prepared to attack everything and not be worried whether he takes marks or things like that. He just needs to get a feel of things," he said.

"Watching him last week, the thing I noticed about him, he just became more and more a spectator as the game went on. Only he would know the reasons why. Even when there was a contest three or four metres away, I just watched him and he was just spectating.

"He has just got to attack the footy.

"He hasn't got to the stage where he no longer has talent or ability. Just at this point of time, that confidence has deserted him and he is not doing the things that made him a really good player."

Koschitzke was taken behind only Riewoldt in the 2000 draft but ahead of fellow top-10 selections Alan Didak (Collingwood), Luke Livingston (Carlton), Andrew McDougall (West Coast), Dylan Smith (North Melbourne), Laurence Angwin (Adelaide), Daniel Motlop (North Melbourne), Kayne Pettifer (Richmond) and Jordan McMahon (Western Bulldog).

That draft also featured Shaun Burgoyne (No.12, Port Adelaide), Daniel Kerr (No.18, West Coast), Drew Petrie (No.23, North Melbourne) and Chris Newman (No.55, Richmond).

"He (Koschitzke) has to get himself absolutely spot on before he has another crack because otherwise he is doing himself a disservice," Maclure says.

"It is just horrifying to watch."