The Juventus midfielder has struggled to reach the heights of his Euro 2012 brilliance so far this season, but Ancelotti said that every player goes through a tough spell.
"Players can go through moments of difficulty," Ancelotti told Tuttosport. "It's not the first time that it has happened.
"Juventus can remain calm because you'll soon see that he will return to his old self."
Ancelotti has also dismissed Zvonomir Boban's call for the 33-year-old to end his international career.
"I don't think that [quitting] will happen at all," he added. "Andrea is very attached to the Azzurri shirt and I doubt anything has changed in that regard."
Pirlo has won 91 caps for his country.