This has shady deal written all over it.
If you're Atleti, what would you rather do?
(a) Sell Saul for ~50m to an English club and use the money to buy a premium young player in a buyer's market?
(b) Help out one of your two biggest rivals by exchanging Saul for a 30-year-old Griezmann and his crippling contract?
I know Griezmann had great success there previously and that Simeone's relationship with Joao Felix is reportedly not great. But the move really makes no sense unless there is some other kind of hidden part of the arrangement. If I'm Atleti, I'm happy that Barcelona is crippled and struggling to register players as it gives me a freer run at the title against next year. The last thing I want to do is help them dig out from their mess.