What do you mean, better? You -- probably -- get better by training. The players' values won't rise, unless there are some sort of "power ups". If you mean team chemistry/compatibility, you need to place them on their right position (or change it with some upgrade thingy), let players from the same national squad/national league play together. I'm sure you knew that already, but I don't know what you could mean otherwise. I'm not sure how much it actually matters in F13, but at at least make sure it's >60% or so, given that F13 can be a very random game with one touch and so on.
Yea I was just confirming that was the case. As far as better I meant can their rating increase if say they are a young player? Other then the random roster updates. Each player has a potential rating from what I was reading some time ago. And maybe a 78 has the potential to be a 92 or something along those lines. I was wondering how that, if that is the case, would work either by playing the players or using the training consumables. Because I have seen players you can buy with different ratings but are the same player.