The Brighton fans, who greatly outnumbered City's in the 71,000 crowd, must have feared the worst in the south coast's club's first FA Cup semi-final since 1983 when they beat Sheffield Wednesday before losing the final to Manchester United in a replay after the first game ended 2-2.
Kevin De Bruyne admitted after the victory over the Seagulls that it's going to be hard for his side to do the quadruple.
Manchester City are back in action this week, as they face Tottenham in their Champions League quarter-final on Tuesday. We are now in the Final of the other and in the other two competitions, we are there.
Despite those regular absences, City remain firmly in contention to retain their crown, and Pep Guardiola's side could yet claim an unprecedented quadruple.
Mendy, whose professional honours include World Cup, Premier League, Ligue 1 and EFL Cup winners' medals, said the flexibility of Guardiola's team was important in the win over Brighton and praised the bond between his team-mates.
"Today, we didn't "conserve energy". We certainly would have seen in the past players clutching their head, rolling on the floor, so I don't think he makes a big deal of it.
"When you achieve 100 points, you can not repeat that".
Guardiola added: "No team can perform fantastically for every single game". 'I know Liverpool is going to win all the games (in the Premier League) so to be champions we will have to win all of our (seven) games. I don't remember, I didn't see, but I think when Sir Alex Ferguson won the treble [with Manchester United in 1998-99], in that case not all the games were fantastic and winning four or five zero.More news: Kieron Pollard’s sensational knock helps Mumbai Indians to thrilling win at Wankhede
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Meanwhile, Guardiola says reaching an FA Cup final would be a huge personal milestone.
Whatever plan Brighton boss Chris Hughton had cooked up to stop a City side who had won 20 of their last 22 matches in all competitions was in tatters after only three minutes.
With City staying in London until its trip to Tottenham's new stadium in midweek, Sergio Aguero had traveled south on Friday but was not risked with a muscle injury.
"I'm probably not [going to be at my best], not compared with a year ago", he told reporters.
"We will have a good rest and we will follow the rules".
"(On Tuesday) We will start the race for the Champions League.
"We are going to try until the end every game". He was disciplined for reporting late for treatment on an injury in September, and was reportedly spotted in a nightclub hours before City's game against Fulham last weekend.