Roberto Mancini has high hopes for Sergio Aguero

Aguero, the club's record signing at 38?million, made a sensational City debut on Monday night by coming off the bench to score twice and set up another goal.

The Argentina forward's performance, which began in the 60th minute, propelled City to a 4-0 win over Swansea in their Barclays Premier League opener.

With Silva and Toure also impressing in the Etihad Stadium rout - and the prospect Aguero could also combine with Carlos Tevez and Mario Balotelli if the pair can be brought onside - City would appear genuine title contenders.

Mancini said: "I think Sergio needs to play more with his team-mates to get better. We have incredible players like David Silva and Yaya, who speak the same language. I think he needs to improve with the team."

The win was a clear warning to other sides with title ambitions, most notably champions and neighbours Manchester United. Mancini added: "It was really important to start very well because United won - but it is always important to start the season well."

Aguero is determined to build on his flying start to life as a City player. Having played in the Copa America last month and starting pre-season training late, the 23-year-old playmaker was held back throughout last week's Community Shield.

The former Atletico Madrid forward quickly set about making up for lost time, and told City TV: "I am happy. The start was really good and I want to keep like this. It was nice."