If City play an attacking XI, their formation will be something like this
-----------Aguero---------------Dzeko----------
-------Nasri----------Toure----------Silva------
--------------------Fernandinho-------------------
---Clichy---Kompany-----Mangala---Zabaleta---
-----------------------Hart-------------------------
(Bony could start in place of Dzeko, Demichelis in place of Mangala and Fernando instead of Fernandinho). All of these players are in great form and they tore Newcastle apart 5-0 with a lineup like this. However, Pellegrini could be afraid of us and want to play a more defensive, counter-focused game, in which case he'd play something like
-----------------------Aguero---------------------
-------Milner----------Silva----------Navas------
--------------Toure---------Fernandinho--------
---Clichy---Kompany-----Mangala---Zabaleta---
-----------------------Hart-------------------------
Milner and Navas both have the workrate and pace to harass Messi and Neymar and then get in behind when Alba and Alves are bombing forward, Toure and Silva can burst from midfield and Aguero is easily their best option up top. I would probably play something like this, seems like a good balance between aggression and caution, although if Pellegrini wanted he could be even more defensive by playing Fernando instead of Silva and Toure farther forward, and even more so by replacing one of the wingers with Kolarov, although as we saw last year, that didn't really work out too well. Should be a really interesting game regardless