For anyone out there who is interested, Tom Tango, author of The Book, has run a study for the past few years that measures defensive ability by aggregating the opinions of fans who watch a particular team.
I'm including the link here for the Padres page, but if you're a diehard of some other team (we'll forgive you for now) you can navigate around. I'll be checking back in to see if your answers are correct. :) Kidding. Have fun with it.