Mbappe was effectively omitted by France coach Didier Deschamps for this week's squad due to form.
Diallo said, "I want to immediately dispel this idea: every time I spoke to him, I always saw in Kylian a lover of the French team, respectful of the shirt you saw. I have no doubts about his total involvement, nor of his behavior as captain and towards the group.
"It may happen that he has a less good shot, but the only wish I have is for him to return to his post as soon as possible, at the head of the France (team).
"Kylian is one of the best players in the world. He's going through a slightly more delicate period, but the desire, I think, of all soccer lovers, is that he get out of it as soon as possible, that he be the player who made us dream in 2018 and 2022, who finds Les Bleus, the captain's armband and takes us to the 2026 World Cup and the search for a third star."