Aguero scored deep into injury time to help Manchester City to a 3-2 win over Queens Park Rangers last season and consequently win the Premier League title, and Mancini believes that he would not have remained at the club if the Argentinian striker had not scored.
Mancini told The Telegraph: "You probably would have been talking with another manager now.
"We didn't win the championship in the last second, though. We won the last championship during all the season.
"Football is beautiful because anything can happen in one game. I hope this year we can get the same result but don't concede one or two goals a game."
Manchester City play Queens Park Rangers on Saturday evening.