Manchester City attempted to downplay talk of another rift with its controversial forward Mario Balotelli after the Premier League champion produced its best form of the season in a 3-0 victory over Sunderland.

Goals from Aleksandar Kolarov, Sergio Aguero, who replaced Balotelli (pictured) after 55 minutes, and James Milner were accompanied by City's first clean sheet of the campaign.

But the game was overshadowed somewhat by the behavior of Balotelli, who sauntered off the field and stormed directly down the tunnel to the City dressing room after being substituted.

City coach David Platt refused to be drawn on a subject over which the club has become increasingly sensitive.

"I don't know," said Platt when asked why Balotelli had walked down the tunnel instead of taking his place on the City bench.

Platt responded in identical fashion when asked if it was normal procedure for a player to walk down the tunnel rather than watch the rest of the match.

And Platt confirmed that Balotelli's removal from the game was a purely tactical decision and not one enforced by injury to the Italian, who has yet to score in the league this season.

City manager Roberto Mancini claimed he was happy with Balotelli's performance.

"Mario worked a lot, he had a chance," Mancini said. "I am happy with Mario. Mario played a good game, I think he can do better."