It was announced on Tuesday morning that the PSG striker will join Real Madrid when his deal expires at the end of the month.
Bernardo told BBC Sport: "From the beginning (at Monaco) you could see that he was different. All I remember is this little boy coming to training to train, he was so young, and one of my best friends in football, Joao Moutinho, after Mbappé's first training session comes up to me and says: 'Who is he? The child. He's special, isn't he? He's got something different.' And in the end he really had it.
"He wasn't shy at all, and when you're 16 and you come to training with the grown-ups... you don't want to humiliate the more mature ones. And instead he destroyed everyone. He didn't care if he was nice, he wanted to score, to score goals. And it's not easy to find something like that in a 16, 17 and 18 year old."