Natural Positions are set completely randomly.

Guru.

aberger wrote: Oh my god... !!! Is it possible to change the natural position? At the moment the setting up of the formations is totally weird

by putting players in the positions you feel they would perform the best they gain experience in that position and in time their natural position will change.

Basically, Natural Position indicates where the player is most comfortable playing. He will have a higher rating when playing his Natural Position.

If you want to put a player in a position due to his skills, remember that his rating will take a while to increase. For example:

Player's natural playing role is Running Back
If really needed, he can also step in as Offensive Lineman, Tight End, Quarterback, Defensive Lineman, Linebacker and Kicker

If he has a rating of 2.5 stars at Running back, his rating at the other positions is not going to be good, seeing as they are "really needed.....". So if you would want this guy to play in the other positions mentioned, it will take a while to change him to that position, as the Running Back rating is so high.

Guru.

I can vouch for it because it's happened to some of my players.

Some for good, some bad. One player was 2 stars, I played him somewhere that his skills suited better, and he changed to that position after about 6 games yet dropped to 1 star. I'm guessing if I play him for a while he'll rise again.
Another player was 1.5 stars, he changed position and is now 2 stars. He actually hit 2.5 in the last game, I assume because he isn't all that consistent (which means he might over or underperform in any given week).

Go into my team and look up transfers, a player called Mads Asmussen. He was a DL when I bought him (yeah, i know, I paid way too much but I was so young and so eager), he is now an OL because that's where I've been playing him.

I`m using good old excel