I posted but A&C chimed in so I edited it out. You made a GREAT point about "replacement dropoff". There is a stat in american baseball, called WAR - Wins Above Replacement. As is suggested by the name it combines a multitude of data to arrive and +/- value for a player related to an "average" or replacement level player in that position. If I could be so bold as to suggest that is the crux of your argument.