Manchester City striker Mario Balotelli (left) scores the opening goal against Manchester United during their English Premier League match at Old Trafford yesterday. City romped to a 6-1 victory.

Mario Balotelli can be one of the world's top three players if he can cut out his eccentric behavior, Manchester City manager Roberto Mancini said after the striker's two goals inspired Sunday's 6-1 rout of Manchester United.

Currently staying in a hotel after setting his house ablaze by letting off fireworks indoors this weekend, Balotelli was equally explosive in the derby at Old Trafford.

After netting a 22nd-minute opener, the 21-year-old Italian lifted his shirt to reveal a T-shirt with the words "Why always me?", leaving Mancini with just one explanation.

"It's Mario," he said at a news conference. "He's crazy but I love him because he is a good guy."

The first goal was pure class as his clinical first-time shot from the edge of the area sped into the bottom corner, while his second on the hour-mark was an instinctive close-range finish after getting on the end of a James Milner cross.

They were his fourth and fifth league goals of the season and he has now scored in four successive games to help City go clear at the top of the Premier League.

He picked up a yellow card for his T-shirt celebration, prompting Mancini to later substitute him in case he picked up a second in a tacit acknowledgment that with Balotelli you never quite know what is around the corner.

The volatile forward picked up multiple red and yellow cards last season and honed a "bad boy" reputation off the field, letting off fireworks from the balcony of his city-center flat, suffering a grass allergy in the middle of a match and drawing publicity for wearing a bizarre hat shaped like a glove.

"The problem is his age, he can sometimes do some mistakes, but as a player he is incredible," Mancini said of his compatriot.

"I hope for him, for football in general, the day that Mario changes his (mindset) ... he will become one of the best players in the world like (Lionel) Messi, like Cristiano Ronaldo."