Bishop
Pedro Mendes
There's nothing stopping 18 starting top tier games. Cubasi is 18 years old, Varane was playing for Lens at 17 and bought by Real Madrid by the time he was 20. History is littered with good enough young players, so the truth either our young CBs are not good enough (maybe yet, maybe never) or the coach didn't believe they were ready again rightly or wrongly.I think it is fair to say we have had young youngsters up to now. Last season our centre half options in an injury crisis, Phillips and Dorrington, were 18 years old. If that happens next season they'll be twenty year olds. In Phillips case he would have completed 2 Championship loans and hopefully be way more ready for 1st team action.
It won't be so long before we have a clutch of U21s who are actually 20 or 21.
Age is no barrier to playing if the playing is of sufficient quality, we've seen that ourselves with Bergvall and Gray to an extent. But obviously the quality has to be there in the first place along with the support and belief of the coach. We haven't had both of these things.
In summary it's nice that we have a number of young players but their age alone is no guarantee of a finished product. If they aren't getting significant minutes now then they might never because if they were indeed talents above the standard they would be playing right now.