haven't tried this...

but I'm guessing the game engine won't let you sack players all your players because of roster limits. Once you get down to 14 or 15 players on your squad, I don't think you will be able to sack anymore

what I have tried and know it doesn't work is

trying to get rid of too many players by placing them on auction. In my early seasons, when I was trying to get rid of the poor players, I only wanted to keep about 12 of the players I had, so I tried putting everyone else on auction, but when I got to 14 or 15 players left on the squad, the game engine wouldn't allow me to place any other players on auction.