Basically, once you sign a new player, a contributive role is assigned to him. A player can have different roles, so can give assists, score, do nothing, be the FKs or Corners man, etc.. by playing against a 1* what you do is to oversize the internal programming till the max. limit distance that the simulator can reach, so a key player will probably score 3-4-5 goals, or whatever. Just try it and experiment, so you can know about the player behaviour.