I'm really struggling for FB's, still. I don't know if I've just got a mind block on or if FB's just don't get the same brutal robbery of their abilities that other positions do.
I think the issue with FBs (to a certain degree CBs as well) is how much different the role is and what makes them stand out.
How many really become WC straight off the bat? A Giggs or a Ronaldo will take your breath away aged 17, while a 17 year old fullback lacks the much needed experience, discipline and positional awareness. They may look like exciting prospects but you have absolutely no confidence in them not cocking it up every now and then until well into their 20s. E.g. Lahm, he was in the German NT for years but only really stood out as he came of age.
Take Shaw for instance. How many young fullbacks are better/more promising than he was before his leg break? Arguing whether he would be absolute top class or just a regular fullback is pointless though, you simply don't know, and yet Lahm wasn't really much better at that stage or was he? Evra was a car crash when he arrived!
The likes of Rafael and Fabio were permacrocks. I don't think it had a noticeable impact in their remarkable attributes, but it certainly didn't help them establish themselves and get the regular and steady playing time that would develop what they lacked.
A forward with technique and vision can reinvent himself leveraging them if their pace and agility is lost, while a fullback losing his pace and agility has little else to rely on at that stage so you most likely never get to hear of them again and simply forget them.
I guess the point is raw natural talent can make for a devastating forward while with a fullback raw natural talent means the jury is still out and will be for some time. Different price tag on
raw and much harder to redeem yourself from its negative consequences.