The Blues and the Red Devils go head-to-head at Stamford Bridge this Sunday, with Ancelotti's side two points clear of United at the top of the Premier League table.
Ferguson commented: "I thought Ancelotti would do well. He was a great coach at AC Milan.
"He won the European Cup twice and brought a wealth of experience with him to Chelsea. He was also a great player, so he has a lot of knowledge.
"He brought a different system to the ones Chelsea have used in the past.
"It has maybe been easier to adapt tactics because they have very experienced players, who have more tactical knowledge than the younger ones.
"It has probably been a bonus for them in that respect and it seems to have worked well."