I don't put too much stock in that differential and its not just errors that matter; it's plays not made such as not turning a DP or throwing to the wrong base, or not hitting the cutoff man (the latter two are more mental errors). Those things also drive up pitch counts, forcing more bullpen use, etc.
I really wonder if these guys think ahead about what they are going to do if X, Y or Z happens. There's a great video on youtube where Dwight Evans describes what was going through is head prior to Joe Morgan hitting that shot that he made that staggering catch on in the Fisk game and all the scenarios he ran through.