Proficient Gs is exceptional. There is no way to guarantee Proficient, it is by design.
Once you hit strong and after 3-4 weeks into the season, if you manage GS well, a player will keep a strong GS or above for the rest of the season 999 times out 1000. If the player drops to 7, it's likely his GS was mismanaged.
If your team is riddled with 7s, you are mismanaging GS.
I agree with the majority of this, except 999 times out of 1000 is too high (at least for my team). It's closer to 900 times out of 1000.
In four seasons, I've only seen 1 player drop from 7 to 6 while playing in the sweet spot of 48-75 minutes.
Dropping from 8 to 7 while getting 48- 75 mins is not likely, but happens about 10% of the time.
Dropping from 9 to 8 happens about 25% of the time, even with well managed minutes.
Strangely, I've never seen a drop when a player gets exactly 48 minutes. Only holds steady or increases.