My second basemen this year (78 97 59 61) made 11 errors (.981 F%) and last year (87 84 59 66) made 10 errors (.977%) in about the same number of games as your guy. Having a lot of GB pitchers can increase the error count because they see more plays. You might compare fielding percentages to see if he does any better there. But the biggest red flag is that you've been playing him at 90% fatigue. I don't have evidence to back this up, maybe someone else does, but it's always seemed to me that low fatigue affects performance in the field more than at the plate. I seldom play guys at the BL level at less than 97-98%