"We've had three weeks of hard training and I've had a better idea of my team now," he told a news conference in Durban on Saturday.
"Alexandre Song may not start the first match against Japan. This does not mean there is anything bad about him. He is a great player. It's just that I want to start the tournament with the most competitive team," the Frenchman explained.
Le Guen's comments came after an hour-long training session for the Group E match, before which he held a 15-minute discussion with the Arsenal midfielder, attracting media attention.
He also said he would be installing 36-year-old Hamidou Souleymanou as first choice goalkeeper in a major surprise given Kameni has been Cameroon's undisputed first choice goalkeeper over the last seven years.
Le Guen gave no reason for the decision, nor did he name any more changes, but public opinion in Cameroon has blamed Kameni for conceding too many "easy goals".
They hold him, together with ageing Geremi and former captain Rigobert Song, responsible for the team's quarter-final exit from the last African Nations Cup in Angola in January.
Le Guen spoke at the news conference of his confidence of a win, even through Cameroon have not won any of their last seven matches.
"I have watched many videos of Japanese football over and over and I know their strongest weapon is that they have very swift attackers," he said.
"We've worked very hard to deal with that and as concerns Monday's match, I'm full of confidence."
His optimism was shared by defender Sebastien Bassong, who accompanied Le Guen to the news conference.
"We are professional footballers, we are used to playing against swift attackers like those from Japan. So they will not pose any problem because we are ready to cope with their style," said Bassong.
