I appreciate exactly where you're coming from on wanting to go for the win. It's a natural thing, and you would have to be a coach very dedicated to his coaching philosophy and the developmental philosophy of his club/school (an enlightened AD would help!).
Giving players minutes vs securing results is a real example of a decision that millions of coaches all over the world face every single day... and one that sums up this particular dilemma perfectly. But every problem presents an opportunity; (I am basing this suggestion on the assumption that the player to be introduced is a weaker player than those already on the pitch)
Can the new player bring information on to his team-mates??
Can you as the coach involve the player in recognizing the weakness in the opponent (be it tactical or in personnel)?
Can you as the coach involve the player in the decision making process which is how best to capitalize on this weakness?
Can you as a coach put faith in your coaching philosophy and in your players, introduce your substitute off the bench and still do it again next week even if it goes wrong?
These, I believe are the questions that you have to ask of yourself and of your players. If you can empower a player to make their own decisions and recognize situations for themselves you are giving them a personal responsibility for their own decisions that will stand to them for the rest of their lives, both on the pitch and off it.
Regarding the coaches you mentioned at the end of your post - I've never heard of two of them, but I am aware of Anson Dorrance (having read the biography "The Man Watching"). His coaching methods are outlined in adequate detail in the book and I think the results are there for all to see. However, I do think that he won A LOT of titles when anyone who could recruit a half decent team had a shot at a National. I do admire him though and his methods (although I would consider them to be VERY dated) have stood the test of time, it is after all, a very simple game. He has very good long standing relationships with all of his players, past and present, which should tell you really all you need to know about the man behind the coach. And, for the record, his fall-outs with the governing bodies only puts him higher in my estimations (I've got plenty of first hand experience of Football Association nodding dogs).
That is not to say that I am being hypocritical either as it appears that I am contradicting what I said at the start of my post - Anson is at the sharp end of athletics; he is in the results business. He does develop his girls of course, but they are there to win championships, the development of course comes in tandem, but their principal aim is to win titles and if they produce some national team players or another phenom like Mia, then thats just an added bonus.
