Baseball statistics have come a long way in the last decade or so, with fans now generally recognizing the value of on-base percentage over batting average, and how RBI totals can be deceiving.
But quantifying defense remains a real challenge. Among the possible solutions are different formulations of range factor, which attempt to measure how good a player is at getting to balls not hit directly at him.
The numbers still don't tell the story, though. Look at this play by Derek Jeter - how exactly would you put it into an equation?
And let's not even discuss the fact that anyone watching Jeter (and many, many other players) realizes that his range tends to get somewhat wider depending on the game situation.