I too like to base past performances as a basis to buy a player. With Scouts, I know it is a throw of the dice as you are buying unproven "talent" but not performance.

Here's my take on negotiating or even buying players off TM that has good track records. They will suddenly not perform once they sign for you and this is because maybe

1. Orders and formation is different.
2. They are simply past it.

Unless you use the same formation or type formation eg. lone striker vs pair you are more likely to destroy the player.