I think there's some overreaction to Duffy being dropped in here to be honest. He's 3 games in to his PL career, so there's no need to get upset about him not getting the experience of playing against City. If he's good enough, he'll have plenty of opportunities in future.
If he were to come in tonight and have a poor game, which is possible and he has made mistakes so far (he's still at the stage where people turn a blind eye at the moment) then that's what could really do the lad some damage. He'll be down about not starting tonight for sure, but I doubt it will hurt his confidence. I'm sure he'll have been spoken to, told he's done well so far but that we don't want to put him under too much pressure when he is so new to PL football.
Youngsters are blooded slowly at EFC, but if they're good enough then they will find there way and stay in. That's always been the case and I don't think there's cause to get too upset on the basis of tonight's team.
By the way, personally I WOULD have started him tonight. I can completely understand the argument against it though.