Happens to me all the time.
Two points:
1) Ultimately its the individual stats which count and not the stars.
2) It must be the training - particularly the individual training.
3) As in real life not every player reaches his potential.
Come to think of it that was 3 points ...
I find that the most useful indicator is value in relation to age. So eg a 24 yo worth 4m is better than a 28yo worth 5.
From then on I look at the stats for the particular position I play them at. I also pay attention to form; I first have the assman pick the team cos they usually do it on basis of morale and form and then manually tweak their selection. But the bigger the squad gets the less I do that cos I have to rotate to keep everybody happy.
All things considered if you get the tactics correct for particular matches that is the most important factor ...
so do you compare the stats when choosing your starting team or do you go by how the game ranks them star-wise?
Don't forget value also depends on League, time remaining on contract, performance etc aswell