When I 'm tanking, I use my worst players vs good teams (playing in their positions) and "mid-table" teams (switching GK with ST)
and my good players vs the crap teams (because it's impossible to loose even if playing oop).
I get domination against those team so get an extra blue.
I don't use at all blues on my crap or non-interesting players, only for the young/good ones because I train them, so low morale can cause injuries to them.
Usually I can save blue packs with that way.