Mancini is convinced their failure was down to bungling last summer's transfer window, most crucially when they were first in for Robin van Persie but dithered, opening the door for Manchester United.
He insisted: "It's important we work well from now until August 31, not like last year. It's not important only to work well on the pitch.
"We must have our targets in mind and then move quickly. We didn't do this last year. We moved so slowly.
"We lost the players that were our targets to improve our team. We should move more quickly.
"It's important to build your team from the basement, when you start in the market you need to buy important players that can help you."