The Argentina international striker scored all four goals in City's 4-1 Premier League win over Tottenham on Saturday, taking his league tally for the season to nine, level with Chelsea's Diego Costa.
It could have been even better for Aguero at the Etihad Stadium, had he not seen a first-half penalty saved by Hugo Lloris.
Aguero has been troubled by injuries in recent months, with a number of muscular problems preventing him from featuring on a consistent basis, but that has not stopped Pellegrini from touting him as a possible Ballon d'Or winner.
"I said that before this game," the Chilean said. "I'm not talking because he scored four goals and I'm not expecting him to score four goals every game.
"But I know him a lot of years before he came here. I saw his career in Argentina and Spain and that's why I said that he's one of the most important strikers in the world.
"It's not because he scored four goals, it's because he has the conditions to be one of the most important and when he's 100 per cent fit he will demonstrate every game."
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