They have a decimal place which you can only see when you go to sell the player.
That's a useful clue but the problem is that you must get the player to make that test.
In auctions, I believe that sorting is the most useful (and probably the only clue we have).
The thing is that the players must have a very close quality so to compare.

For example, your player Ashour, DL-DC about 62% quality, after some good training maybe will have the same value (129.3) with Oliver when he 'll be 95% or 115%.