Ancelotti has already told the 21-year-old that, despite his efforts on Wednesday against MSK Zilina, he needs to improve still further.
"He played an important game on Wednesday and scored," conceded Ancelotti. "It's not important for me if he's playing in the Champions League or the Premier.
"He's a Chelsea player with good quality. He could do better. I expected more of him on Wednesday and he knows this.
"He has fantastic ability, and I'd like to see these skills and ability more in a game. He scored with fantastic movement, but we need to see more of that."