Forgive me if this is something already posted and known, I did search but found nothing on it.
Players cut during the preseason using "cut days" will not count against the salary cap penalty.
I took the Lions, but didn't want Stafford. I usually would go into the rosters under My Madden and dump him off there to avoid the 20 million penalty that comes from dumping him in franchise. During a second season Bengals Franchise I got a random rookie placed on my team, as the game does at the start of the Preseason.
He turned out so good that I didn't want or need the Free Agent MLB I picked up. I wanted to cut the MLB I got in the Free Agent bidding war...but i was afraid to eat the 5 million bonus money.
So, anyway, I ran a Franchise with the Lions and when the first weeks cut day came i picked Stafford to cut.
Then I simmed the rest of the season, and went to the Off season.
I checked the financials, and found I had no penalty. That 20 million was just smoke.
I don't know if this was intentional, although I personally like it. Helps out with not having to hold on to an overpaid vet while waiting to see if a rookie pans out, and having to eat that bonus when you dump him off.
Hope this info is helpful. It makes me look at the free agency and draft differently now, knowing I can survive if I make a bad choice because I can use the cut days to dump off a player.
Since most rookies are added without a bonus, you can always dump them from the player management screen and be fine.
Oh, and a side note. You can play the entire pre-season over cap. I was 19 million over cap and it didn't force me to correct until the regular season started.