The Premier League leaders booked our place in the last four with a hard-fought victory at Goodison Park, breaking another record of 17 away games unbeaten in the process.
Guardiola's men left it late to snatch victory though, as Ilkay Gundogan and substitute De Bruyne struck in the final minutes of the game to seal our place in the last four of the competition for the third successive season - a feat we had not fulfilled since 1934.
"We knew how tough it would be," he said. "The FA Cup away, against Everton.
"We were in Budapest in the week. They were incredibly committed from the beginning. We knew it.
"They defended incredibly well and have pace with Richarlison and Dominic Calvert-Lewin. Every throw is like a corner and they have big players, like Mina!
"These games need patience. We knew the team who scored would win the game.
"All the players were fantastic and Riyad and Kevin in the last minutes could change the rhythm. We found the goal and we are in the semi-final. We knew it would be one of the toughest games we would face.
"At 0-0 in the second half, I talked to Rodolfo and Juanma. about what we can do.
"Sometimes, with substitutions you are 100% sure with what you have to do; sometimes, you have doubts and if you have doubts, you take more time to do it.
"The game was under control. We maybe just needed fresh people. They run a lot - they were incredible defensively, and aggressive: Allan, Gomes and Sigurdsson run a lot. They were aggressive.
"At the end, we decided on Riyad and Kevin and they changed the rhythm a little bit and fortunately, Ilkay Gundogan was in the place he has to be as a striker or attacking midfielder to score a goal."