JAStewart

Like, cause certain players are underrated (Nani potential 158) and I was wondering if you trained them hard their potential would change? Like in real life?

I've never known it to work, but I've never really checked before.

Younger Crayola

No, potentials are static. As they should be.

FrazT

There are almost no circumstances when the in game PA can or will change apart from a long term, very serious injury and they are very rare in the game, so in essence the answer is no.

If you feel a players PA is low, you can use FMM editor to up it.

JAStewart

Aye I'm not too keen an cheating, 'tampering' if you will, but I don't actually play as Man U so its not a problem as far as Nani is concerned

olivne

even long term injuries will not affect a player's PA.
They can, however, lower his CA massively which could lead to him not being able to fully reach his potential

SCIAG

Nani's potential is -9, so it look's like he's been given one at the lower end so the bracket in your game.