Our own devil_fingers spent an inordinate amount of time creating his own methodology to evaluate catcher's defense based on throwing out runners, preventing wild pitches and passed balls, throwing errors, and catching errors. Not surprisingly, the three Royals backstops fared poorly: Pena was -2.9 runs in limited playing time, Buck was -4.8 runs in more playing time, and Olivo was 113th out of 114 at -8.8 runs (thanks Mike Napoli).
R.J. Anderson of Fangraphs and D-Rays Bay takes a quick look on players who have been essentially average this year. "Borrowing" the idea from somebody else "appropriately named Devil_Fingers," he lists a few average players, some surprising (Jason Bay? Really!), some not (Mark DeRosa), based on Wins Above Replacement (WAR). The Royals' own Billy Butler gets a shout out.
One player who missed the cut was Adam Dunn, who despite mashing the ball this year, is still below average because he plays awful, awful defense in both the outfield and at first base. If Dunn was a DH, however, he would actually be average to slightly above average.