The England goalkeeper was dropped in favor of Costel Pantilimon after a series of high-profile mistakes, and the defender knows that players must push themselves.
The England international goalkeeper was dropped for his side's 7-0 Premier League demolition of Norwich City on Saturday, and the Argentine feels Manuel Pellegrini has the luxury of being able to choose from two players at every position.
"The manager makes decisions," Zabaleta told the press. "We know in this team now the performance of everyone should be good week in, week out, because we have two players in each position who can play. Sometimes mistakes might cost [someone] their place, but we are a big squad and we need to try to do well to keep the place in the team."
Zabaleta reserved special praise for the club's attacking players after their masterclass at the Etihad Stadium against Chris Hughton's beleaguered men.
"It was a great result, 7-0, especially for the strikers - Kun [Aguero], [Alvaro] Negredo, [Edin] Dzeko," he said. "Yaya [Toure scored] another fantastic free kick. We needed to respond well after the Chelsea defeat. I think it was a great performance by the team."
City currently sits fifth in the Premier League, six points adrift of leaders Arsenal.