You're comparing his performance at 3B vs 1B; it's not a linear calculation. 2+2=5
as 3B Miggy is the worst, as a 1B the thing could change.
Miggy -14.6 at 3B Vs Machado, Longo, Beltre, Lawrie, Arenado, Donaldson, Frazier, Moustakas, Wright.....In this group Miggy is s***.