When you have two players in each position, with one as the more regular starter and the other regularly on the bench its hard to see where the third choice gets any game time.
If pantillimon, lescott, milner and dzeko are regularly on the bench and then a game like today comes along to rest the regular starters you can't play youth and still not give game time to the four I mentioned (and others in the same situation) or they're never getting any games and would leave straight away.
Ideally, up front for example, we'd have 3 strikers who were as competent as each other (as opposed to one partnership that works far better than any other combination). So maybe aguero as the main man and then two who could happily play alongside him to similar effect and would get equal amounts of game time and then a guidetti in the wings for days like today.
There are games where I'd rather have a young hungry striker coming on as sub, or starting in a game like today, than a dzeko trying to force his way back in and feeling the pressure of that.