The controversial striker came off the bench to inspire City to a 2-0 win over Everton at the Etihad Stadium.
Until his arrival after an hour, City had been struggling to break down the Toffeemen's obdurate defence.
But Balotelli brought renewed focus to City's attack, scoring the opener, which flicked off Phil Jagielka, before fellow substitute James Milner wrapped up the points late on.
Far too often in his short City career, Balotelli has been in the headlines for all the wrong reasons.
His most recent escapade came on the pre-season tour of the United States when he was hauled off during a match against LA Galaxy for showboating.
However, Balotelli proved there was no bad blood remaining between him and Mancini by racing over to his manager for a hug having netted his first league goal since February. And now his boss is expecting big things.
"Mario can make a big contribution this season. I am sure of this," said Mancini. "His behaviour has been so-so. But he is a good guy.
"He likes Manchester City. He likes English football.
"Sometimes when he scores, he is unhappy. Today he was really happy. Today he knew he scored an important goal."
It also proved Mancini correct to introduce Balotelli ahead of Carlos Tevez, who remained on the bench throughout.
However, the City chief admitted a four-match European suspension that rules the striker out of Tuesday's Champions League trip to Bayern Munich played a part.
"I needed a player who could also play on the right side," said Mancini. "We needed to open up the defence, plus Mario can't play against Munich on Tuesday."
Balotelli has now scored in successive games, having opened his account for the season in Wednesday's Carling Cup win over Birmingham.
More importantly, Mancini's multi-talented squad proved themselves adept at overcoming difficult opponents, who had won the last four meetings between the sides and deployed Jack Rodwell to man-mark David Silva.
"Today was difficult," said Mancini. "Everton defended behind the ball for all the game. It was not easy for us to find space.
"We had to push them for 90 minutes. In the end, we deserved to win the game. I am delighted with the players."
Everton manager David Moyes made no apology for the limited tactics, believing his team were badly done to when a throw-in he felt should have been in favour of his side went against them in the build-up to Balotelli's opener.
"I wasn't going to come here for the enjoyment of Manchester City," he said.
"I was going to come here and do what was right for Everton.
"I have to praise the players for how they went about their task.
"They have done a lot of really good things. For long periods we kept them at bay."
And Moyes was not impressed by Vincent Kompany's tackle on Tim Cahill in a clash from which the Everton man received a yellow card but also limped off injured.
"It is a terrible tackle," said Moyes. "I have seen it again. His foot goes right on his shin. I am disappointed it wasn't spotted."
Source: Team Talk
Source: Team Talk