Narrow 4132 - What midfield trio to pick?

[MeMyself2k13]

Question regarding this formation - Mezzala or CM-A?

I don't fully understand what systems benefit from a Mezzala. I'm also worried about my right flank if I use one, especially because it's vulnerable as it is already, since there's no cover from wide midfield.

Alternative option is to change my AP to Attack duty and use CM-S on the right. That would be a better option defensively, I guess.

Also, if someone could explain a difference between CM-S and Carrilero in this formation, I'd be very thankful. I tried using him one match, but I was under the impression that he was being very defensive - is Carrilero therefore more suited to systems with attacking Wing Backs, or did I not get it right?

[Dingusen]

I played that formation ealry on in my save, before I got the players I wanted, and used to Mazzalas in Midfield. Tried 1 carr ond 1 BoxtoBox but there was not enough space between my midfielders. Was a little reluctant to try Mazzalas as I feared they would work properly being a new role... but eventually tried it and...wow. By using 2 mazzalas you get proper spacing between then and the DM and AP, they work great with WBs and gives your system some needed wide (wide-ish) play.

About support or attack duty for mazzalas, its alot about balance of the entire team, and also how much risk you want to take. Personally I find that A-duty is about too much, they will often be too far in attack to help in defence, but maybe you can live with that having a DM on D-duty.