Coman withdrew from Les Bleus' XI to face Moldova on Friday after experiencing a problem during the warm-up, prompting head coach Deschamps to replace him with Matuidi for the 4-1 victory.
Coman only recently recovered from a hamstring injury and Deschamps said he would not be unnecessarily risked against Iceland on Monday.
"Kingsley felt a little problem with his back and it pulled him a little at the thigh," Deschamps told RMC Sport. "He could not move freely.
"I'm not here to take chances. I have no problem using Blaise, who did not disrupt the collective."
Deschamps said Coman's injury was less severe than that of Lucas Digne, who also pulled up with a thigh problem ahead of the clash with Moldova.
Everton full-back Digne was an unused substitute while Layvin Kurzawa played on the left side of the defence, and Deschamps said: "Kingsley seems to be less problematic than Lucas.
"Lucas felt a complication in his thigh. There is no injury but it was not possible to use him."
Goals from Antoine Griezmann, Raphael Varane, Olivier Giroud and Kylian Mbappe delivered a comfortable victory for the world champions in Chisinau.
They can make it two wins from two if they beat Iceland on Monday and Deschamps has urged to side to avoid any complacency.
"We could have scored more," he told fff.fr. "But these matches are still complicated. My players handled the game the right way. We did not fall into any trap.
"All the attackers scored, so much the better.
"A lot depends on us [against Iceland]. We have the quality, we all saw that.
"We did not give Moldova time to organise and to get back, and we have to keep it that way because the second match is coming in three days."