I disagree totally.
I'm french and i did follow Mendy since Marseille before he went to play for Monaco. His attribute has never been the pace but the timing. Mendy has nothing to see with Walker which attribute is really pace. Mendy has two qualities: the timing and the delivery(pass).
His problem actually is not physical at all but mental. He didn't play for almost two years cause of the two injuries(knees), he just need time to have the confidence back. When you don'y play for so long of course you lose the confidence. Mendy is not finish at all , he should play more to have his confidence back but it will be hard cause Zinchenko is a hell of a player (even if people don't really realise)
Sorry for my english , i'm pretty sure i've made huge mistakes.