[Curtis]

I was just checking out a text file I downloaded a couple of years ago that gives numerical explanations for fielding ratings at different positions. Interestingly, range and error ratings are more highly valued at first than at second(!), and turn double play is more highly valued at second.

By extrapolation, I then come to wonder if your first baseman had a good TDP and a poor range and error rating. If so, that might explain it.