the way ive understand it is that it mainly influences how well the player can perform, the stars shown for each player, its also called BPOS. The higher talent the higher the BPOS can get, you can look at BPOS at how well a player knows the position. Talent also influences how fast a player gains BPOS or following my own analogy; learns a position. Secondly it also sets an overall cap for all trainable non physical skills.

In trolling the forums ive found this one:

Talent (stars)---Non phySkill cap-----MAX BPOS (stars)
-----0.5-------------------11-----------------3----
------1--------------------12-----------------3----
-----1.5-------------------13----------------3.5---
------2--------------------14----------------3.5---
-----2.5-------------------15-----------------4----
------3--------------------16-----------------4----
-----3.5-------------------17----------------4.5---
------4--------------------18----------------4.5---
-----4.5-------------------19-----------------5-----
------5--------------------20-----------------5----

ah that makes sense why some of my players that have .5 talent are only at rating 3.

read the 'read this before you do anything' thread, there's much useful info, written by very attractive people in there..