If the player is already green for you, or if the player was projected to be in a division below yours, the message you get back will be from the player instead of the scout. The short answer is, if the players response includes the word upside, he has good potential.
if you search for 'manifesto' in the gd forum, somewhere down at about the 2nd or 3rd page of the thread is the key for all the scouting responses. It includes the responses from the players.