The England striker, who has scored 14 goals this term, has been sidelined with a hamstring injury.
No time frame has been given for Calvert-Lewin's return, and Ancelotti says his team must cope without their star forward.
"The next games are really important if we want to stay in that position [among the Premier League frontrunners]," said Ancelotti ahead of facing Wolves on Tuesday.
"We are going to play away games against tough teams, we need to get results to stay in that position.
"It will be difficult, we have players out – but we have the squad to manage these kinds of games.
"Without an important player like Dominic, we have to be able to replace him in a different way.