Manchester City came from behind to ease into the FA Cup quarter-finals with a 5-1 win over SkyBet Championship side Huddersfield Town at the Etihad Stadium.
Aguero and substitute Kelechi Iheanacho completed the scoring in the second-half to send the hosts through to a Quarter Final clash away to Middlesbrough.
He said: "Of course the start was positive because we went in front but we were not at our best, performance-wise.
"We have shown too much respect, unfortunately, against a very strong Manchester City side.
"Congratulations to Pep -the result was fair. We made too many easy mistakes when we had the ball and when we defended we were not aggressive enough.
“When you play against Manchester City you have to be very aggressive."