The Premier League champions were keen to add Robin van Persie to their ranks, but the add Dutch international moved to Manchester United from Arsenal in August for £24million.
Mancini aired his frustrations over City's transfer policy, controlled at the time by Football Administrator Brian Marwood, as Van Persie opted for the red half of Manchester while the Blues did not add to their roster of strikers.
Ferran Soriano's appointment as City's new chief executive came late in the transfer window, while Marwood moved to oversee the club's new training ground and Academy facility when Txiki Begiristain was recruited as director of football in October.
"The transfer market is always difficult," says Mancini. "We were also in a difficult period. We changed the CEO, the man who was in charge in that moment. If you are not strong enough you can have some problems in the transfer market.
"For us the market was really difficult and our problem for now is to improve our strikers.
"Anything can happen in the transfer market. You can want to buy one player but it is difficult because the player then makes another decision. We can't change that.
"We have four strikers who scored a lot of goals last season and we just need to work."
Mancini is now calling on the four strikers who helped City win the Premier League last season to raise their game, starting with Sunday's Manchester derby, in their bid to retain their title.
Sergio Aguero, Mario Balotelli, Edin Dzeko and Carlos Tevez have scored 19 times between them in the league so far this season, with only Balotelli scoring in open play during their last three matches.
"It's always the case that you can have one striker in a difficult spell during the season," Mancini added.
"Usually, when you have four strikers, two or three of them are not scoring but one is. But at the moment we have four strikers who can't score.
"This can change maybe on Sunday and after that it will be OK. But we need to work more. Our season depends on our strikers. If we start to score like last year we will have a big chance."
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