If you're selling a player who is 5* to you, he'll appear to managers in the same league until 2 leagues above. On the market, you can see players rated 3-5*.

If you want him to appear to lower level managers, he will have to be maximum 4* to you, then he will appear as a 5* to managers directly below you.

And try not to sack your players from now on, you just lose your money, and they will find out the true quality of your players with just one click to your squad page. If anything, I would keep lower quality players to make your team seem weaker, then they will underestimate you and put out a weaker side.