how bad would it be? A d-/d-/d- rated catcher who played in 1 game. I know people would steal at will but how many passed balls, errors?

Progressive issue.

D- covers a very wide range. Some are borderline playable, others might make a ton of passed balls.

I had 1995 Dave Nisson (D-/D-/D-, .811 Fielding and 2.81 range) in a progressive. I platooned him in the catcher position since he only had 330 ABs. The results were horrible. I think he ended up with around 10 errors and around 40 passed balls. The team was super competitive and still made the playoffs but I didn't start Nisson at catcher at all. Even a tired catcher was better than what Nisson put up.

Long story short - I once played the 1990 Cecil Fielder (the very good season) at Catcher for the year and won the division. Oh yes, LOTS of steals and passed balls. It can be done.

I was going to draft Keith Moreland, and he would have caught for me in 1983 with a triple D- rating but very good hitting. Someone else grabbed him, though.