Ancelotti believes the 27-year-old could play a key role for Chelsea this season.
He said: “The goal at Spartak Moscow obviously improved his confidence. He is playing continuously now so he is showing some good football and he is working for the team.
“He was consistent last week against Wolves and he was consistent again today. Last season he showed he was ready when he replaced Ashley Cole.
“He is a very efficient player and I think he has a future.”