Yellow/Red Cards

[KT Cole]

You also need to take in to account individual players Aggression Levels. I've found that if it is higher than some other skills [i.e. Fitness, Strength] it can also produce higher/more chances of getting Yellow and/or Red Cards, more so if you have your Tackling set to Hard. When I train my players I aim to keep Aggression levels as low as possible, if they are getting too high for my liking, as you could raise that level too much and thereby increase the risk/chance of your players getting suspended. Huge problems further into the season as games can be lost with players being suspended/unavailable because of issues like this.
Also, IMHO, I think that there is coding built in to the game that "mimics" referees, inasmuch as you can get ref's who do "love to wave Yellows/Reds. Likewise it's the same with Free-kicks too. So beware when setting tactics, especially if you're not going to be online to play the game yourself, especially if it's an important game for you. So I suggest you look at your players Aggression Level and see if you can lower it if possible. I alter my Tackling in the game, if I'm watching it, and adjust it to suit the team I'm playing and also to keep better control/possession when playing.
I sometimes train my players using the old version of the game and add Skills where I want them to be added, rather than the new version of the game that adds them automatically for you.

[nash123]

Aggression doesn't matter, I think. I got a player with 7 yellow cards this season, who has his lowest % at aggression: 88% (overall % are 132%). My highest aggression guy is 163% (overall 128%), got no card at all.
I also have a 98% aggression-guy, who recieved only 1 yellow card and a 143%, who recieved 5 cards...

I think it's only this season, because I collect all (important) data after the season is over:
This season, my squad revieced 33 cards in only 38 games, last season I played all 52 games (won triple) and my squad recieved only 21 cards. The squad is nearly the same (only a new AML is in the squad).
The season before were also all 52 games played, recieved only 23 cards.