City came from behind on Saturday to win the fourth round tie 2-1.
Guardiola said afterwards, "We played a really good game, it was a typical FA Cup game - that's why this competition is unbelievable. We knew that they were strong and they'd run in the channels. They are a really good team and incredibly well managed but we created a lot of chances. I'm happy to go through."
On whether he felt his side struggled in the first-half, he insisted: "I don't think so. The first 10/15 minutes maybe but after the fantastic goal that they had - we took the game and created a lot of chances."
On whether he was frustrated that he had to bring on Phil Foden and Kevin De Bruyne, Guardiola also said: "Absolutely not, that is why they are here. We talk this competition incredibly seriously and we thought it was the best decision to make. I am happy for Kevin's goal, his movement was really good."
On Nico Gonzalez's injury, the manager added: "Welcome to the Premier League and the referees. Maybe he knew about the referees because I understand it's not easy. It's not easy to do something when you play against teams like in League One."