Commons is out of contract at the end of the season and his immediate future remains uncertain with Celtic unwilling to meet his demands for a new two-year contract.
The 31-year-old playmaker, Scotland’s Player of the Year last season when he scored 32 goals for the champions, has only started five of Celtic’s last 19 matches under manager Ronny Deila.
MacLeod, the former Celtic midfielder and assistant boss who won five championships with the club, admits to being bemused by the limited game time being given to Commons this season.
With Aberdeen having emerged as credible title challengers in recent weeks, he insists Celtic could be making a costly mistake if they off-load Commons during the current transfer window.
“It could make the difference between Celtic winning and losing the league if Kris Commons leaves this month,” said MacLeod.
“If he did leave this month, to replace him like for like with a younger version would cost around £4 million or £5m. But a younger version of that quality is not available to come to Scottish football these days.
“You would find it difficult to replace Commons. There are not many players aged 23 or 24 who are going to get you between 25 and 30 goals a season like Commons can.
“I think the Kris Commons situation at Celtic is the strangest situation in football just now. I watched him last week at Kilmarnock and, by a country mile, you would pay money to watch him more than any other player in Scotland right now.
“Even compared to someone like Alexei Eremenko, who is a terrific player for Kilmarnock, Commons was just miles ahead. He scores goals. Celtic are looking for a goalscorer just now and with John Guidetti off form, the manager doesn’t know who to play up front.
“Stefan Johansen is a good player, but he can’t fill that goalscoring role just off the front in the same way Commons can.
“It is a poor situation when you have Scotland’s reigning Player of the Year who is still desperate to stay at the club, yet they are making it difficult for him.
“At some point, if it doesn’t happen, he will go. He will be squeezed out of the door if he doesn’t get what he wants.
“Celtic are a poorer side without him, there’s no doubt about that. He is the one player in the team who has got a spark.
“Against Kilmarnock, he was hitting balls from all over. He hit the bar twice, had a couple saved by the ’keeper and curled one just past the post. He was involved in everything and he lifts the team.
“If you are playing in a team that is having lots of attempts on goal, then everyone wants to get involved. If you are in a team where it’s just pass, pass, pass without having shots at goal, you go nowhere.
“If Celtic continue in the form they are in at the moment, not scoring enough goals and with Guidetti not scoring, they are under pressure. Commons is better than anything else they have, yet he doesn’t get a start every week.
“They have got to look at that. They have to look at the system they play. Johansen is playing where Commons played last season. Commons has been a revelation in that role and Celtic need to have him there.
“I think a deal can still be done with Commons, but it’s up to the club. I don’t know whether it is Ronny Deila’s intention just to let him go. Sometimes the manager has an influence on the board and he has to make sure Commons stays.
“With contracts for players over 30, you have to make exceptions for exceptional players. He is only 31. He is fit, he’s not injury-prone, he is always ready to play. Even players in my era, if they weren’t injured, played on until they were 34 or 35. When Commons is in top form, Celtic are a better side.”
Deila has expressed his desire to make his squad leaner this month with fringe players such as Teemu Pukki, Amido Balde, Derk Boerrigter and Beram Kayal among those who could be moved out on a permanent basis.
“I think they have to clear the decks,” added MacLeod. “Ronny has got a massive squad and a lot of them are not getting a chance. So what’s the point of keeping them?
“Just move them on, save a wage and bring in something better than what they’ve got. They have to bring in players who will go into the team and make a difference.
“With Aberdeen putting in a challenge just now, Celtic have to start thinking about bringing in better quality. Over the last two or three years, Celtic fans have been waiting and looking for better quality.
“If it doesn’t come in this month, then it’s going to be a real challenge. If you spend some money on a player of real quality who fits in right away, then he is going to make the difference when it comes to winning the title.”
• Murdo MacLeod was speaking at the launch of Level5PR, a new media relations and sports management company in Glasgow.