Originally Posted by dfs
I think the biggest misunderstanding about numbers w/respect to baseball is the two fold uses. Are you trying to explain what happened or are you trying to predict how valuable a player will likely be in the future. There a big chasm between those two uses.
That's a place to start. Oh, and good for you for trying to learn something.
This is very very true. Even advanced proprietary formulas like PETCOTA aren't much better at predicting a team's upcoming season as some of the more simple formulas.
Bill James projects Jay Bruce hitting .263/.342 /.518. Don't think of this as a hard prediction, but something more like the average performance Jay Bruce would have if the season was played a thousand times.