City came from behind to win 2-1 thanks to Haaland's brace.
“It’s unbelievable. Nine now this season, I think that’s more than my best tally I’ve had in the Premier League, and he’s done it after four games,” said Grealish.
“He’s an unbelievable player, an unbelievable person. He gets everything he deserves because he works so hard on and off the pitch.
“He’s just an absolute machine in front of goal and I can’t speak highly enough of him.
“We all know that he’s had a difficult week, him and his family. I send all my love to them. It does speak volumes about him as a person and his mental strength.
“To come out there today and perform like that and score two goals for us to get the win, I’m sure it’s everything that is family would have wanted. I can’t speak highly enough of him for that.”