Manchester City manager Roberto Mancini said his team must improve despite easily beating Wigan at Etihad Stadium.

Sergio Aguero scored a hat-trick and Carlos Tevez missed a penalty in the 3-0 win, meaning City have scored 15 goals in four league games this season.

But Mancini was unhappy at the number of opportunities they wasted.

"We had 15 chances in the first half and we scored only one goal - this is a problem because the game can change any moment," Mancini said.

"Next time it's better if we close out the game in the first half. We need to improve because we have started the season very well but the season will be long.

"If we want to arrive at the end of the season still at the top we need to improve."

Aguero has now taken his total to six goals for the season, and although he outshone Tevez in terms of goals, Mancini said he was still pleased by the former City skipper's performance.

"Carlo is not 100% at the moment but I am happy for him because for me he played very well with Sergio," added Mancini. "He missed a penalty but this can happen - usually he scores.

"It was important for him to start, to play and to play well and maybe in two or three games he will be 100%."

Edin Dzeko was rested for the Wigan game as City prepare for their Champions League debut on Wednesday against Napoli.

Gareth Barry is the only injury concern, after picking up an ankle problem, but Mancini hopes he will be fit in time.

"I hope we will have Gareth back for Wednesday," he commented. "We have no other injury problems but they are so tired as they all played two games for their national teams and we need to recover in the next three days."

Wigan boss Roberto Martinez said his team had been taught a lesson, but admitted they showed Mancini's side too much respect in the first half.

"Probably, we were overawed by perception of Manchester City and I think we gave them too much respect and we were punished," he said.

"But in the second half we learned a little bit quicker and even though we conceded two goals we were more ourselves, but overall it was a harsh lesson and we need lessons like this to fulfil our potential."

Wigan lost a record of seven Premier League games unbeaten, stretching back to last season, and although Martinez praised City's performance he said his side could also improve.

"It's a day to give Manchester City credit, they played fantastically and they deserve the three points," he added.

"But we don't focus on the opposition. We need to focus on us, and there were certain things we did well but we are a young group and we are a lot better than we showed today."