The 19-year-old Paris Saint-Germain hitman has enjoyed a significant rise to prominence during the tournament, notably for his sparkling last-16 display in the 4-3 victory over Argentina, during which he scored twice and won a penalty.
There were, however, fears he might miss the St Petersburg showdown against their neighbours after he missed a session along with Samuel Umtiti, N’Golo Kante and Benjamin Pavard, who have also been stalwarts of Deschamps’ starting XI as France have gone deep in the tournament.
The coach moved swiftly to cut these worries down, though.
“Even if four players were missing from our session today as a precautionary measure, everyone will be available for tomorrow,” Deschamps told the media.
Greater worries had been reserved for Barcelona centre-back Umtiti, who has been fighting a slight knee problem for the duration of the competition in Russia. Again, though, Deschamps was bullish over the Lyon academy product being available.
“Like all the players, they could have a little worry that dates back to playing with their clubs during the season,” he said.
Benjamin Mendy, who is another to have had knee issues, was back training with the team, however.
Earlier in the day, Mbappe had been the subject of a social media prank from Mendy, who took a photograph of his sleeping team-mate on the flight.
The Manchester City man commented: "Too much Razmokets."
When a Monaco player, Mendy branded Mbappe 'Razmoket' - the French translation of children's television programme 'Rugrats' - as he was so young.
Paul Pogba and Antoine Griezmann were also in on the act, which came as a form of revenge for the Atletico Madrid attacker, who had been similarly pictured sleeping by Mendy, with Mbappe mimicking one of Griezmann's goal celebrations. On that occasion, Mendy said: "Too much Fortnite last night."
France face Belgium, having lost 30 and won only 24 of their previous meetings. They have not, however, lost any of their three major finals matches against their near neighbours.