Rabiot was overlooked for Deschamps's 23-man squad for this summer's World Cup, but the Paris Saint-Germain midfielder was included on the standby list.
The 23-year-old made a request to be taken off the list of reserves, however, and Deschamps has admitted that he was "surprised" to learn of Rabiot's stance ahead of the competition.
"It was not a letter sent, it was an email that arrived Monday late afternoon. I became aware of its content. Of course, Adrien signed it," Deschamps told reporters.
"I called him to have a confirmation that it was he who had sent this email. He did not answer me. I got confirmation from my manager. In the process, I warned my president of the content. I also warned the president of PSG because he is a PSG player.
"I was surprised of course. I can understand the disappointment, the immense disappointment, but to take such a position... we are talking about a young player who for a while was in the French group. He excludes himself from the team.
"I dare to hope that through some decisions like this it will allow him to mature, to reflect. I am convinced that he made a huge mistake in taking such a position. He refuses his status as a reservist, to follow a program, and if there was a problem of being called as a substitute. It is his decision he assumes."
Rabiot, who has appeared six times for the French national team, scored five times in 49 appearances for PSG during the 2017-18 campaign.