City landed £16m Javi Garcia, £12m Matija Nastasic, £6m Scott Sinclair and £3m Maicon yesterday to go with earlier £15m buy Jack Rodwell.
Mancini said: “I was frustrated, as it is difficult to do everything in one week or 10 days.
“When you finish the season, you have a meeting with the club. You talk about players but sometimes it is not possible to take all the players you want.
“You should have a different choice. But getting these players we have bought, I am happy.”