[Crapshoot]

Hmm, if we're working under the impression that its to be limited to three variables- lets discard speed- it is already taken into account in other things (such as Steals and Speed itself), so no need to add one specially for defense.
1. Arm strength- absolute neccesity- valid at every position; should be a factor in defensive switches, especially if it towards the right on the defensive spectrum.
2. Arm accuracy- Same as above.
3. Range- Some people can get to more- this should be a comibnation basically of Speed, awareness, and general baseball intelligence (an idiot would play Bonds in at 2nd )...