Don Mattingly boss card glitch?

When I put him at 3B, which is supposed to be one of his secondary positions, the lineup screen shows his fielding drop all the way down to 8. Is this just a weird visual error or does it actually impact his in game performance?

That would reflect out of position penalty.
but with 3B as a secondary it shouldnt be that.

It's because he is a lefty. He shows up as gold fielding in game

Wouldn't recommend a lefty thrower at 3b