[One Great Matrix]

My general take is:

If you can play catcher, you can play catcher.
If you can play first base, you may be able to play 3rd base.
If you can play second base, you may be able to play short with a strong arm.
If you can play short, you may be able to play 2nd base.
If you can play 3rd base, you may make an OK 1st baseman.

If you can play left field, you can probably play right field, and maybe center if you have speed.
If you can play center, you can probably adjust to the corner outfield positions.
If you can play right field, you can play right field.

And learning the outfield is a lot easier for an athlete than learning any of the IF positions.

Other adaptations should be based on history or future projections, & not as you brought up here with Guidry just because a guy played a few innings at a position.

And also as you brought up one of the biggest oversights is when you train a player at a position, they sometimes become better at that position than at their primary position. At best they should become as good. The other thing to address is maybe a player wasn't spectacular at a position but he did play it regularly. If he played it regularly and was not particularly weak (forced into that role because his bat was valued and there was nowhere else to put him), there might be a secondary rating for real-life experience that keeps a guy like Guidry from playing a better CF than certain versions of DiMaggio. That is their rating based on how well they played or are projected to play there plus(+) an experience rating where they are either comfortable or not at the position (if they had a lot of real-life experience there for that season or career for career cards.) If not, the player's blunders or mental errors would be higher for players who have trained up or could project to play a position but have no real experience there.