The Argentine has not featured for Manuel Pellegrini's men since picking up a hamstring injury in a 5-1 Premier League victory over Tottenham on January 29
Aguero has not featured for City since picking up a hamstring injury in a 5-1 Premier League victory over Tottenham on January 29, but is deemed fit enough to start.
Asked when he had made the decision to start Aguero, Manuel Pellegrini told Sky Sports: "During the week. Sergio worked the whole week normally.
"Maybe [he won't play] for the whole match but he had no problem to start."
In goal Pellegrini has kept faith with first-choice cup goalkeeper Costel Pantilimon, while Martin Demichelis once again partners Vincent Kompany ahead of Joleon Lescott.
Asked why he had favoured Pantilimon over Joe Hart, the City boss replied: "It's very difficult for me to decide. All the players deserve to play.
"Pantilimon has had a very good Capital One Cup and he has also played well in Premier League. It's a good chance for him."
Gus Poyet's Sunderland team includes former Manchester United players John O'Shea, Wes Brown and Phil Bardsley, as well as former City fringe player Adam Johnson.
Manchester City starting XI: Pantilimon; Zabaleta, Kompany, Demichelis, Kolarov; Nasri, Toure, Fernandinho, Silva; Aguero, Dzeko.
Sunderland starting XI: Mannone; Bardsley, O'Shea, Brown, Alonso: Cattermole, Colback; Ki, Larsson, Johnson; Borini.