those are the "fast trainers", the players that gained more than the other players of the game.
That means if you spend some extra greens (and reds ) you can develop them as 6* players very soon.
If they are playing good in the game, that's another story.

(check if you want my guide, to see the higher prices and some other useful posts
http://forum.topeleven.com/tutorials...ers-chris.html ).