Balotelli, 20, stepped off the bench to score the winner in the 1-0 play-off first leg victory against Timisoara in Romania.
He swept the ball home from close range after being set up by Emmanuel Adebayor in the 72nd minute.
"He had a great debut and I am happy that he scored. He is a good player," said City boss Mancini.
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"He needs to improve of course and get to know everybody. It was the first time he had played with the team."
Balotelli, however, picked up a booking after losing his cool and was told by Mancini not to repeat his actions in England.
The Italian warned: "We must work on this with him because it will be different in the Premier League than in Italy."
Balotelli needed treatment at the end of the game but should be available to face Liverpool at home on Monday.
Mancini said: "We do not think it is serious. It was probably just a kick, it is not a problem."
Source: PA
Source: PA