In my opinion, game shape is one of the most hard things to get managed right in BB. I tnink it's just unfair if there is a random finger in it, because it's enough challenging to make one player get the "correct" range of minutes (between 50 and 70, as far as i know) in one week.
If there isnt a big random factor in game shape - and i hope not - my theory goes with some kind of history in player's minutes through his career. Just look at these numbers, taken from my roster, starting this season.
Player A, weeks 1, 2 and 3: 12,57 and 31 minutes ; game shape 7,7 and 8;
Player A has always been a bench player. He never played too much minutes but can manage to get always around 7 and 8 in game shape (but never 9!).
Player B: 72, 52, 74 ; 7, 7, 7
My best player, a tipical starter. Maybe around 65-70 min/week average through his career. I had always get him around 8 and 9 in game shape along the seasons.
Player C: 67, 52, 76 ; 7, 8, 9
A tipical starter as well, although maybe he averages around 60 min/week. Look at minutes for player B and C. Almost identical, although player C had increased GS from 7 to 9, while player B remained at 7.
So, if past weeks minutes are considered in GS formula, and if there isn't a big random effect in it, i can say that player's history minutes average - maybe some seasons - can have some effect in players GS. Maybe some deviation from those average minutes (look at those 52 min in player
can make a decrease in player GS, i don't know...
I just don't want anyone to say "oh nevermind, there's a random finger in it, just make them play between 50 and 70 and pray".