Boyata made his debut and Weiss only a second senior start and Mancini was pleased with what he saw.
"I have never been afraid of giving young players there chance in the side. It is important for us as a big club to know that we can rely on the younger players if we need them," he told City's website.
"Vladimir has shown what he can do in a couple of substitute appearances and Dedryck has been doing really well in training.
"For me both young players have bright futures and that is not just good for them but also the club. It is important to me and to the owners and to the fans as well that we continue to bring players through our Academy."