The strength of the Player downgrade by 20%

Hi,

I noticed in the last 2 end seasons that I didn't get to the next level because i ended not between the last eight teams (this season ended in nine place)
and still the strength of the players downgrade by 20% as happen when the team move to the next level in he end of the season.
can you tell me why it's happening?

Thsnks'
Shimon

9th position many times promotes to the next level.