2. Sergio Aguero vs. Jonny Evans
Judging by what happened against Reading, when United's defence shipped 3 goals, Sir Alex may actually opt for Chris Smalling to partner Rio Ferdinand at the heart of the United defence, but Evans is the most senior fit centre-half behind Rio, and experience may count double against the energetic and pacey Aguero. Either way it will be the deputy at centre-back who looks after Aguero, given Ferdinand's comparative lack of pace, and in Aguero they will face their toughest task of the season so far. He is nimble and not afraid to run at defences, and his vision for finding space around the box is one of his key skills. He might not have scored in the past three, but United's defence have shown they are far from water-tight recently. Sir Alex will no doubt be lamenting the lack of Nemanja Vidic in games like this.