Ancelotti believes the game could prove decisive in each side's season and admits that he finds Mancini a difficult manager to overcome.
"He's a very intelligent coach who prepares a tactical game very well,'' Ancelotti said. "That's the reason I have difficulty against him. I hope to change that on Sunday.''
Ancelotti and Mancini have a friendship dating back to their playing careers. "We were team-mates in the national team - he's a friend,'' Ancelotti said. "Not such a friend because he's won too many times against me.
"He has to understand that he is my friend, so sometimes he can give his friend something.''
Mancini also proved his fellow Italian's nemesis towards the end of the pair's time in charge of AC Milan and Inter Milan, respectively, and has now won six of the last seven head-to-head clashes between them.
With Chelsea and City boasting the biggest-spending owners in English football, Ancelotti and Mancini are arguably the most under-pressure managers in the country.
"This is normal, managing that pressure, for the coach," said Ancelotti. "It's one of the skills a coach must have in football.
"The second thing is to be patient, not just with the players but with the club and the journalists. It's a good skill to have, patience, a very good skill.''
Ancelotti is hoping to beat Manchester United in the Champions League for a second time when the two sides meet in the quarter-finals. He knocked the Red Devils out four years ago when he was in charge of AC Milan.
"It was a fantastic evening for Milan and a bad one for Manchester," he said. "They were surprised by the way we started that game but it was a tie that was always in the balance.
"Winning the Champions League is not an obsession for Chelsea, it is a dream. At Milan the Champions League was the most important thing every year. We didn't focus on winning Serie A.
"Losing to Inter Milan last year was a bad moment for everyone at Chelsea. Now we have to see if we deserve to be in the semis again."
"I am always happy to play against United because you know it will be a fantastic game with fair play. Sir Alex [Ferguson] is one of the greatest managers ever. What I like most about him is that even though he has won a lot of trophies he has always maintained his humility."