sorry but your question was who should be starting for juve
i wouldn't say he is too young...
first of all i think he is no rb (and he is acutally a cb) his crosses and passes are awful and he makes silly mistakes....he seems a bit to slow or to big i don't know it looks weird how he moves and he falls so often/slipping
he def has talent but sure he needs more games/experience....
but i don't think a team like juve that is aiming for cl (with a squad hardly good enough) can afford those mistakes