The England star was a constant nuisance for the visitors' backline as goals from Raheem Sterling (2), Aymeric Laporte, Rodrigo and Phil Foden saw City move three points clear at the top of the league table.
Grealish, who played the entire 90 minutes at the Etihad, was proud of the team's response just days after the heart-breaking Champions League exit in Spain.
"We always knew there was going be pressure on us especially after midweek," he said.
"We bounced back perfectly. We stuck together as a unit which was needed. Now we need to try and end the season strongly.
"We just have to go out there and win every game ourselves, we’re in the driving seat. We can’t look at what is going on around us. We just have to go and win every game.
"Fingers crossed, we have to go back and work hard as we have another huge game on Wednesday."
The 26-year-old played a key part in the last two goals of the afternoon, setting up Oleksandr Zinchenko to assist Foden for the fourth, before teeing up the fifth for Sterling.
The 5-0 win now sees Pep Guardiola's side boast a better goal difference of four than title rivals Liverpool and Grealish believes that despite it being a good advantage to have, getting the victory is the key.
"It’s common sense, we know and look at the table," he admitted.
"You see it yourself. The main thing was going out there and getting the win.
"We played against a good Newcastle team who have been brilliant especially since January. Today was the perfect response and perfect performance.
"It's football you just want to score goals, I try to score and assist as I haven't had as many as I want this season. As the game went on we wanted more goals."