Mbappe's absence from training just hours before the game set tongues wagging in Russia and we now know why the PSG star wasn't present during that session.
Deschamps confimed that Mbappe injured his back getting out of bed on the Monday morning, with the teenager hearing a cracking sound before being bed-ridden due to the pain.
The player called for the team doctor, who confirmed that he had put his back out, damaging three vertebrae in the process. That led him to miss training, but the staff were in no mood to be without their star man against the 'Red Devils'.
"The medical staff did everything they could. I don't know how he put his back out. Anyway, it had loosened up sufficiently before the game. Obviously it could have gone again afterwards, but there wasn't any concern about that," Deschamps revealed.
Despite the concerns, Mbappe did indeed manage to start the game against Belgium and showed no sign of the problem, even bursting away from a couple of players down the right wing inside the opening minute.
According to Deschamps, though, Mbappe continued to suffer from some discomfort even until after the final, during which he lashed home a wonderful low strike from range.