Manuel Pellegrini claims Sergio Aguero is worth as much to Manchester City as Lionel Messi and Cristiano Ronaldo are to their clubs.
And despite Aguero's stunning form for City this season, manager Pellegrini is convinced the Argentinian is going to get even better in the coming years.
Aguero continued his outstanding start to the season with a sensational hat-trick in City's dramatic 3-2 defeat of Bayern Munich in the Champions League in midweek.
The prolific Argentinian has now scored 17 goals this season and is again being compared with Barcelona star Messi and Real Madrid ace Ronaldo, the pair long acknowledged as the best in the game.
Pellegrini said: "Well of course I think that no-one can replace Messi at Barcelona, Ronaldo at Real Madrid or Sergio here - or a lot of very important players. It is not the same playing without Aguero as with Aguero. He has many years more to play here. I am always asking and demanding that he tries to be the best player because he has all the conditions to do that.
"That is why I am very glad for him he is always improving every day.
"I think he is a top player, a very important striker here in the Premier League and we are very glad to have him in our team."
Aguero (26) is set to make his 100th Barclays Premier League appearance since joining City for £38million in 2011 as the champions travel to Southampton this weekend, with games against against Sunderland and Everton to come in the next week.
Pellegrini said: "Yes, it is an important game because we need the three points and we can be in the second place. I hope after the three we can be near to Chelsea."