What matters here, is that the best player of the opponent team, and your worst player you use in the main 11, have to have a distance of 180%
Because the simulator, reach a distance of 180% to do the simulations, this means that if your worst player is +180% from the best opponent team all your team will be considered 180%. So i your worst player is 5* and the best is 9* both will be 9 stars from the opponent perspective and this means, that you can compare both players, your 5* or 4* you bought and the 9* being in the same star.
Thats how you expose the internal programming, so you can know if the 4* you bought is better than a 9* you currently have.