An SA doesn't 'de-value' a player.

Your 'mistake' was trying to add an SA to EVERY player in your squad.

If you'd focused on their quality, they would have held their value and still have been high enough quality to play in your next season.

Nearly every one of those players would have had an extra star in quality.

But...the early levels are all a learning curve, I guess you were too hasty and had to learn the hard way, but you could still give the competitions a good go even with the players you still have