Koschitzke was banned for three matches after a high bump on Swan Nick Malceski in round one, opening up a spot in the forward line for Saturday night's game against North Melbourne.
But Lyon said competition for spots was so tight that no obvious candidate had yet risen his hand.
"I'm not locked in," Lyon said before the training session on Thursday afternoon.
"We've got some strong forwards but we want to see how everyone trains because it's so even, the training performance might see the nod given."
Athletic tall Rhys Stanley was a standout in the Saints' pre-season campaign, but played only 30 minutes in last week's VFL practice match.
Nevertheless, Lyon said he would be closely scrutinised along with some others.
"He's certainly in contention and he'll train tonight. We've got a few youthful forwards: (Paul) Cahill, (Tom) Lynch, Stanley and (Nick) Heyne. Is it one of those, or is it (Michael) Gardiner or (Ben) McEvoy who goes forward and maybe (Adam) Pattison in the ruck?"
Lyon refused to admonish Koschitzke for getting suspended and instead praised him for going in hard and making body contact.
He said he had not spoken to his players in any great detail about the finer details of what makes an illegal bump since the match review panel found Koschitzke guilty.
“I quite like aggression. I don’t think it went too far but you find the balance from the modern game,” he said.
“It was a big man playing big so we’re certainly not going to take that away from Justin or anyone within the group. You don’t want to be losing too many along the way.”
North Melbourne was one of only three sides to defeat the Saints last year but Lyon said the memory of the round 21 defeat cast little shadow on this year’s match.
“There were some lessons to learn from that. It stood us in pretty good stead going into the finals. There were some issues to come from that and that helped us get going,” he said.
“It’s a long time between drinks. The relevance of it to today bar a few technical things isn’t great. We’re coming off a strong win interstate. We’re fit and pretty much available. We’re looking forward to the challenge.”
