Roberto Mancini recognises the FA Cup is the best chance for silverware this season following last weekend's Premier League defeat to Southampton which left Manchester United 12 points clear at the top of the table.
The City boss named a strong starting eleven for the visit of Championship side Leeds and the decision paid off within five minutes when Yaya Toure latched onto Carlos Tevez's neat flick and rounded Jamie Ashdown to open the scoring.
Aguero was awarded a penalty by Mark Clattenburg ten minutes later when he was brought down inside the box by Tom Lees and the Argentinian forward placed the spot-kick into the top corner, sending Ashdown the wrong way.
Leeds boss Neil Warnock made two changes at half-time but his side never looked like finding a way back against the Premier League champions.
Tevez rounded off a wonderful City move on the goal-line seven minutes into the second half to put the game beyond doubt before Aguero completed the rout with a composed finish from David Silva's through ball.