Tweaking without revising

All coaches have a system. They run a particular style of offense and defense, and if they are smart they recruit to those systems. However, you do not always get the players you target, and sometimes injuries upset the formula. So, coaches have to tweak their system to suit the group of players they have. They have to do it without a wholesale revision to that system to the extent that they have to "start from scratch" and start developing and teaching all over again. I suspect it is a fine line sometimes.