Much of the credit for helping the Red Sox win the World Series went to a more scientific approach to baseball statistics, dubbed "sabermetrics" by its greatest proponent, Bill James. But one aspect of the game has defied quantification: the number of runs individual fielders save. Traditional fielding statistics count errors and plays made, but not hits fielders 'should' have reached. Major League teams have recently addressed this gap using proprietary records of the location of every batted ball, but the underlying data has been kept secret and will never exist for the first century of...