When in a chaotic and unpredictable environment, you depend on the ability of your brain to quickly process all that is going on around you. This is called processing speed.
Subconcussions can reduce the speed at which you are able to process the information that is sent to your brain. This ultimately slows down the speed of your reactions and limits you from performing at your highest level.
This is why it is so important to train to maximize the function and utilization of all four of your situational awareness systems. Each of these systems communicate with your brain, and you want that communication, processing, and response to be as fast as possible.