Manager Pep Guardiola believes the form Manchester City have shown in the last four months is one of his side's greatest achievements.
A 2-0 win over Everton after goals in the last six minutes from Ilkay Gundogan and substitute Kevin De Bruyne, who only came on in the 80th minute, saw City secure a third successive FA Cup semi-final spot for the first time since 1932.
It was a 25th victory in 26 matches and kept them on course for the quadruple.
"When you have won a lot of games in four months you are able to adapt and adjust and that is what I am pleased about the most, it is the most difficult thing," Guardiola said.
"It is the mental strength to be ready for every single game. November to March is the toughest period in England and what we have done is more than remarkable, it is incredible.
"It is one of the greatest achievements we have done together for a long time.
"We haven't won anything but we will go game by game and see how far we will go in the competitions."
Guardiola said he was fully prepared for a difficult match and that was what his side got as Everton were defensively resilient throughout and only the late introduction of De Bruyne broke their resistance.
"It was the FA Cup away against Everton and they had all week to prepare and we were in Budapest (in the Champions League) in midweek," he added.
"They were incredibly committed from the beginning. It is so difficult, they had eight players to defend. Every throw-in is like a corner, a real tough game.
"The games should be played like we played with patience, with no mistakes, because if they had scored a goal it would be almost impossible to win.
"We knew the side who scored first would win the game.
"The players were fantastic and with Riyad (Mahrez) and Kevin, at the last minute, we could change the rhythm and at the end we found a goal and got to the semi-final.
"We knew it would be one of the toughest games we would play this season.
"The most important thing was we didn't make a mistake, we didn't concede.
"All the players were incredibly focused and committed on what they had to do."
Defeat ended Everton's hopes of a first trophy since 1995.
However, manager Carlo Ancelotti could not fault their performance.
"Of course we are sad because we are out of an important competition, but to be honest I thought we did the best we can and so there are no regrets," he said.
"We competed really well for 80 minutes against, in my personal opinion, the best team in the world at this moment.
"I am proud of my players because they did the best."