John Dewan, the CEO of STATS, Inc. who moved on to found Baseball Info Solutions, has written "The Fielding Bible," with contributions from Bill James. We have all struggled with quantitative analysis on defense, but this isn't some statshead thing created in a cellar at MIT. James explains that Dewan's aides "watched video from every major league game and had recorded every ball off the bat by the direction in which it was hit [the vector], the type of hit [ground ball, fly ball, line drive, popup, mob hit, etc.] and how hard the ball was hit"
I'm going to have to check this book out at some point...fielding is the hardest of the three major areas of player performance to accurately evaluate objectively, and it sounds like Dewon has made some interesting progress in that area.
According to the book, the Rangers had the best defensive first baseman in baseball last year, but also the second worst defensive middle infield (behind the Jeter/Cano Yankees), with Soriano and Young both rating amongst the three worst defensive players at second and short, respectively, for the past three years.