Mario Balotelli's remarkable talent for finding new ways to embroil himself in controversy resurfaced on Manchester City's pre-season trip to Los Angeles when the Italian was substituted in disgrace only 30 minutes into a friendly against LA Galaxy.

Balotelli then became involved in a touchline row with his manager, Roberto Mancini, and angrily threw a water bottle on to the pitch after taking his seat among the substitutes.

The striker had gone clean through on goal a few minutes earlier but, rather than finishing off an easy chance, he turned full circle, flicking the ball behind his legs and trying to score with a backheel. It was a remarkable act of self-indulgence and, as the ball went wide, several of his team-mates, particularly Edin Dzeko, could be seen remonstrating with him.

Balotelli had opened the scoring from the penalty spot but Mancini was so incensed with the showboating that he immediately signalled for James Milner to replace the former Internazionale striker. The manager studiously ignored Balotelli as he was substituted only for the player to confront him and demand to know why he had been replaced. Mancini rose to his feet and started to berate him angrily before Balotelli stalked off.

"I hope this is a lesson for him," said Mancini, who hopes a deal for the Atlético Madrid striker, Sergio Agüero, can be done in the next four or five days. "In football you always need to be professional, always serious and in this moment he wasn't professional. He needs to understand his behaviour has to be good in every game – not just in a final or a semi-final but every game.

"He knows he made a mistake. Football should always be serious and if you have a chance to score, you should score. If you are serious, you can play 90 minutes. If not, you can come and sit by me on the bench. Mario is young, I want to help him and that is the end of it. To take him off after 30 minutes is enough punishment. It won't have been easy for him but it has to be a lesson."

Asked what Balotelli had said to him, he replied: "It was in Italian. In English I would find it difficult to give you the translation. But Mario is streetwise, he knows he was not offside."

Mancini's attitude towards the 20-year-old reinforces the sense of a manager who is not going to indulge anyone in his determination this season to have a side with genuine aspirations of challenging for the major honours. Balotelli scored 10 goals in 28 appearances after signing for £25m last summer, but he also picked up 11 yellow cards and two reds and will be suspended for the team's first three Champions League games because of the sending-off against Dynamo Kiev that contributed to City's elimination from the last 16 of the Europa League.

Balotelli's list of misdemeanours since joining the club has been long and extensive, including a training-ground fight with Jerome Boateng and an internal inquiry after he was seen throwing darts at youth-team players from the window of a training-ground building. Even after his red card against Kiev, Balotelli became embroiled in an argument with City's supporters, getting out of his car as he left the ground to remonstrate with a group of fans in the street.

Mancini still firmly believes the good outweighs the bad but their relationship has been fractious at times and, elsewhere in the club, there is little patience for a man whose final act last season was to fly back to Italy – against the orders of his employers – and miss the club's player-of-the-season awards dinner as well as the FA Cup parade. For that, Balotelli received a heavy club fine and another lecture from Mancini about the importance of growing up, making the most of his undoubted talent and taking more responsibility.

Balotelli had taken off his City shirt before leaving the pitch at half-time and did not re-emerge for the second half of a 1-1 draw in which David Beckham played the opening 45 minutes for the home side. The Galaxy substitute Mike Magee scored the equaliser in the 53rd minute before City won 7-6 in a penalty shoot-out that ended with their goalkeeper, Joe Hart, scoring the winner. Mancini's team now head to Dublin for a weekend tournament, with a game against Inter arranged for Sunday.