How is Coach Rating calculated?
Each coach starts with a Coach Rating of 150 for every official Blood Bowl roster. If you attend a NAF sanctioned event using a particular race, your NAF ranking for that race is then activated. When you win a game, you gain Coach Rating. When you lose a game your Coach Rating is reduced.
The neat part is that your Coach Rating is adjusted based on the how tough the opponent was. For example, if you lost to a very good coach then you lose less Coach Rating than if you lost to a worse coach.
If you play at NAF sanctioned tournaments, then the larger the tournament, the larger the potential change in your CR.