When you managing more than 1 team and they are sharing the same server. WITH all your teams you are farming greens constantly.
In ideal case you have 3 teams (or more? I dunno! Upsellers correct me if i wrong!)
Sooo:
step1: You buy a cheap player with your lowest level team... You feed with greens until...
step2: Your higher level team could (seeing from her/his POV is low star again) BUY it for minimal tokens.
step3: Repeat green feeding until your HIGHEST level team could buy... and soo on.
And thats the way you can create a MUTANT player whos having 1% greys (lower than 1% for real) and high white skills with not high avarage%
This is upselling (and creating mutant player) in nutshell.