Ratings are a reflection of a pitcher's trade value in keeper league fantasy baseball pools. They reflect a players predicted performance taking upside, injury risk and consistency into account. These predictions also include a statistical evaluation taking historical and current numbers, age, role and positional flexibility into account.  Injury is of more concern than age for pitchers than hitters. Holds as well as saves are considered in this ranking. I encourage all leagues to have holds to give a larger number of talented set-up men significant value in fantasy pools. 

Basically, if you are in a keeper league, this is a combination of analysis and educated opinion based on my statistical model of a player's 'trade value'.  Naturally, individual trades would depend on the direction you are currently taking your team.