Lionel Letizi will play instead of McGregor.
Le Guen said: “Lionel will play against Inverness. That is my line of conduct.
“It is not easy for Allan because he did very well and played some very good games.
“Allan is not happy but I am not there for them to be happy.
“I think he will stay respectful, though, because he knows it is an honest decision.
“When you do not play, you are less confident. But the most important thing is there has been a discussion between us.”
He added: “It is not easy for Allan because he did very well and played some very good games.
“I was not surprised and I was aware he is a good keeper but Lionel did well before his injury.”