Players need these minimum ratings to have a displayed rating at that position:
https://spreadsheets.google.com/pub?...en&output=html
I never really considered it a bug, since the player can still play the position. It's more that the player's overall skillset is not (or no longer) suited to playing some positions and this is the Interfaces way of warning you. Players change and the game is telling you that this guy is suitable for playing 1B, not 3B, 2B or SS.