Whend i buy a player i look to quality and market value, both depending on the age of the player.

After being in the team, i look to there performance, number of goals scored, assistes, MOM, number of times there name appear on commentaryes.
I dont look to mutch to ratings, most of the time they do not make sense. Quality is relative, If i have a 3* player playing better that a 5* he plays more. Most of my players are sold with 2* or low 3* or If they play bad.