My WR4 gave up a sack in a preseason game, which made me immediately question everything I know about game planning. Turns out he was subbing in as my RG. Why? I have no idea either.

https://die-hard-fans.myfootballnow.com/watch/1700#317931

I assume that since it's preseason and I pulled my starters that I ran out of OL. (This brings up a point about how the 60 player cap is also stupid, but let's not digress.) Why is my WR subbing in for my RG?

Other players that gave up sacks that game: QB4 and WR7.

I quit watching at this point or there may have been more. I'm not sure.

The AI will never do this unless your depth chart is completely empty + there are no available players at that position. Looking at your team I am not really sure why that would have happened, you should have still had plenty of OL even after they were subbed out ... they were all active, yes?

Yes, but it was preseason and the starters had been pulled by that point.

Ive run across this as well. And only in pre-season.

One thing you can do is sign some OL scrubs for the preseason to slip em in your depth chart and just cut em after the final pre-season game. Practice squads will be good for this I think.