Roberto Mancini believes Manchester City would still be in the title race and the Champions League if he had secured all of his main transfer targets last summer.
The City manager wanted to bring Robin van Persie, Eden Hazard, Daniele De Rossi and Javi Martinez to the Etihad Stadium.
But he missed out on all of them and City signed Jack Rodwell, Javi Garcia, Scott Sinclair, Matija Nastasic and Maicon instead.
Only Nastasic has been a success for the defending champions, who are 15 points behind league leaders Manchester City and who crashed out of the Champions League after only taking three points from six group games.
But while Mancini has admitted Manchester United have won the Premier League, he thinks City would be challenging their local rivals at the top of the division if they had done the business he wanted.
"Yeah, sure, 100%," he said. "Probably we would be on the top and could win the second title and probably we would be in the Champions League quarter-final.
"We had a chance to get three or four players who could improve our team but we didn't in the end. Now it is finished."
Instead of signing for City, De Rossi stayed at Roma, Martinez moved to Bayern Munich, Hazard joined Chelsea and Van Persie signed for Manchester United.
"These players made a difference in their teams this year," Mancini added.
The City manager believes a lack of incision in attack is the reason they are so far behind United, citing the draws with West Ham, Chelsea and Arsenal and the defeat at Sunderland.
He added: "This year the difference is only the goals we didn't score. The difference if we score maybe 15 goals more, probably we would be top. We are missing important goals in games we deserve to win easily: West Ham, Chelsea away, Sunderland, Arsenal at home. We lost a lot of points because we didn't score enough goals. This is the difference."