this answer won't help you, but it is the truth, at least as far as i see it. i have had D fielder play quite well, better than A's, who i was resting. If there is any true rhyme or reason to it, i certainly don't know what it is. By the same token, i have hired A+++ guys who were worth every penny (prior to the update). Many championships have been won with the .333(?) Vizquel and the .403 OBP Weis at SS, coupled with the .335(?) Castillo at 2nd. Same holds true for fielding, in my experience. i have used D- guys who killed me, and D- guys who did as well as A+ guys, who they rested. but there is consistency, i believe (but can't say as absolute fact) in who will outperform their ratings. I have no idea how to search those outperformers out, i found a few by trial and error.