The Premier League champions are currently second in the table with 25 points from 11 matches, two points behind leaders Manchester United.
"It's true that we don't have the same flair in the games as we had last season and we've scored less goals for sure," Aguero told City's official website.
"But the Premier League table says something different. We are very hard to beat, we are second in the table and defending well, so we can't be doing that badly, can we?
"We have been hindered by a string of bad injuries to important players – David [Silva], Pablo [Zabaleta], Javi Garcia, Micah [Richards], Joleon [Lescott], Maicon, [Gareth] Barry, [James] Milner, Samir [Nasri], myself."
Aguero added that City can "repeat" their form of last season and retain the Premier League title.
"It's not simple when they all happen simultaneously and I think I'm correct in saying we had very few injuries last season," said the Argentine.
"If we have been succeeding even in spite of these difficulties, then it makes me believe that the best is still to come and we'll be able to repeat our form of last year."
City host Aston Villa at the Etihad Stadium in the Premier League on Saturday.