The Brazilian stepped up in Aguero's absence against Burnley, scoring two goals in the 4-1 victory at Turf Moor.
Speaking to Amazon Prime after the game, Guardiola said: "Of course it's not easy [replacing Aguero] but the team doesn't have doubts about him.
"As a striker sometimes you score, sometimes not. We need the quality of the players up front to make the difference.
"Of course we need him. The strikers are there to score goals and we need him. His effort, commitment, which is always there, but of course, strikers like him and Sergio live for goals, it was important.
"We played a good game. Controlled them, didn't concede much, except one action in the first half and a goal in the last minutes. We played really well. The quality of our players made the difference."