Mancini revealed yesterday he thought he had persuaded Van Persie to sign for Manchester City four months before the Dutch striker was unveiled at Old Trafford in August after completing a £22m move from Arsenal.
MISSING Those goals, including last-minute winners against Southampton and City themselves, have been worth a total of 19 points for United, and Mancini believes City could pay for missing out on the 29-year-old's signature.
"At the moment, he is the difference between us," said the City manager yesterday. "He has scored 14 Premier League goals and it is clear he has changed their situation.
"We were very close, three or four months before he went to United.
We wanted Van Persie because we knew he was totally different from our other strikers.
"We wanted to improve our team, particularly for the Champions League. We were very close to signing him, I know what the reason was (why he did not sign) but I won't say.
It was not about money." Van Persie said he had listened to "the little boy inside him" when deciding to join United on a four-year contract worth £250,000 per week – the same terms handed to Wayne Rooney two years ago.
Speaking at his official unveiling press conference, he said: "In these situations, when you have to make a hard decision in your life, I always listen to that little boy inside me. What does he want? That boy was screaming for Manchester United." When pressed to explain why he thought Van Persie chose to move to United ahead of the champions, Mancini added: "I don't know if he listened to his heart. He took his decision but three or four months before that we were there. We were very close and we were sure it would be very good for us, but it didn't happen and now we can do nothing about it." City's four strikers – Sergio Aguero, Carlos Tevez, Mario Balotelli and Edin Dzeko – have contributed 23 of City's 38 goals in the first 20 games of this season, 12 fewer than United have managed from the same number.
Chelsea and Arsenal have also scored more than Mancini's side yet the Italian declared himself satisfied with his forwards, despite missing out on Van Persie.
"I am happy with my strikers because last season they scored more than anyone else in the Premier League," Mancini said.
"But when you can improve your team with other top players it is important to do it. With Van Persie you can sometimes play three strikers." If Mancini is feeling under pressure after falling seven points behind United, then he was not showing it yesterday as he publicly wished Alex Ferguson a happy 71st birthday.
How RVP has put City strikers in the shade
ROBIN van PERSIE led the scoring charts for a second successive calendar year in 2012 and has outperformed all of City's forwards this season.
MOST PREMIER LEAGUE GOALS 2011
35 Robin van Persie (Arsenal)
23 Wayne Rooney (Man United)
MOST PREMIER LEAGUE GOALS 2012
27 Van Persie (Arsenal/ManU)
21Rooney (Man United)
MANCHESTER FORWARDS 2012-13
Van Persie (United)–17 goals in 24 games (0.71 goals per game)
Sergio Aguero (City)–9 in 23(0.39)
Edin Dzeko (City)–9 in 25 (0.36)
Carlos Tevez (City)–8 in 25 (0.32)
Mario Balotelli (City)–3 in 15 (0.20)