Our expectations for each player are built on some combination of historical track record, cognitive bias and hope. Fighting against those are the realities of probability and random variance. But the biggest obstacle to the realization of our expectations is the fact that every player starts the season at zero.
Consider: We might think that, at minimum, Nelson Cruz is a 35 home run hitter. But right now he's at zero. History is mostly irrelevant, as he has to start building back up to that 35 HR expectation. What obstacles might stand in his path as he begins the six-month trek? Will he get hurt? Will age start playing a factor? Will some hotshot rookie start infringing on his playing time if he goes into a slump? All these variables need to be considered before we can ink in "35" on our cheat sheets.
What if we were to strip away all the biases and hope? What if we were to look at each player's track record holistically, as a single body of work, and let probability drive the expectations?