Mancini said he was still looking and learning from the 69-year-old Scot as he marvelled at his rival's sustained hunger after 25 years and 12 Premier League titles at Old Trafford.
Mancini's City side face United in a highly-anticipated meeting of the Premier League's top two on Sunday afternoon.
The 46-year-old told reporters on Friday: "I can say thank you to him [Ferguson]. I have a big respect for him as he has won everything for 25 years, he is a teacher and I am a pupil. At his age he wants to continue to win and it is not only [a lesson for] me but all young managers.
"He is 69. After 69 years and every three days he is there concentrated, every time they score a goal it's incredible.
"It is difficult to arrive at this age and have the same strength every day, to want to win every game, and want to work every day, it is not easy after so many years."
Asked if he could emulate the Scot and still be coaching at 69, Mancini added: "That won't be easy."
Big-spending City climbed two points above United at the top of the Premier League last weekend and have made their best start to a season for 114 years as they pursue their first league title since 1968.
Mancini added it was a "very important" test for his team.
"I think it will be very different - for the first time in a long time we can go there on the top, this is a good thing for us," he said.
"Sunday will be a very hard game, United at home are incredible, it is important that we go there and are ready to play a good game and defend very well because they have fantastic strikers."
Mancini took heart from his team's last-gasp 2-1 win over Villarreal in the Champions League on Tuesday night - the kind of victory that is United's trademark.
He said: "The mentality is important. United have this mentality, they try to win in the last seconds."
United, with their 19 Premier League titles, and a glittering history, have cast City in their shadow for decades and Mancini knows City's work has just begun if they want to stay above them.
"United have an incredible history, always on the top," he said.
"We are there now and if want to stay there we need to continue to work. We have improved a lot from last year but have to continue to improve. Is not easy to get to the top but when you get there, you have to work more.
"To come away from Old Trafford winning and be top of the league [would be] very important."
Manchester City have only one of 28 league matches at Old Trafford since Denis Law's famous back-heel goal gave them a 1-0 victory there when United were relegated from the old First Division in 1974.
Their only win since then was in February 2008 on the weekend that marked the 50th anniversary of the Munich air disaster when they beat United 2-1.
