The central midfielder has been a key member of the Toffees team that is pushing for a Champions League spot this season.
Ancelotti may get a lot of credit for their success, but he says that he owes a thanks to director of football Marcel Brands for signing Doucoure.
"When we started to talk about the transfer window, Doucoure was on the list of the club," Ancelotti told reporters.
"He was not on my list, but we talked together and we both agreed to sign him.
"I think it was, after six months, a really fantastic signing because Doucoure is playing really well."
Ancelotti added: "Doucoure is really good physically and he's able to recover really fast, really quick.
"He doesn't show problems with his physical condition.
"He has played a lot of games but he is still really good, fresh, and has no problems at all."