And Drogba underlined his importance to Chelsea's cause when he notched his 14th Premier League goal of the season with a powerful header from Branislav Ivanovic's cross against Fulham at Stamford Bridge.
If Ivory Coast reach the Cup of Nations final on 31 January, Chelsea will be without Drogba and Kalou for four Premier League matches and an FA Cup third round tie against Watford.
However, Ancelotti is confident he has enough depth in his squad to cover the absence of his premier striker.
"In some matches we can change the system," added Ancelotti, who is also without striker Nicolas Anelka because of a muscle injury.
"We've played the diamond in every match but we can use our wingers in some matches. Florent Malouda or Daniel Sturridge can play. It depends on the match."
It was not a good December for us but that month is finished and now we look forward to January
Chelsea boss Carlo Ancelotti
And despite their December blip, Ancelotti believes his team can emerge stronger after their run of poor form.
"With this performance we finished a difficult period for the team," stated Ancelotti.
"This could be an important victory in the season because I'm very happy with the reaction of the team during a bad spell.
"It was not a good December for us but that month is finished and now we look forward to January.
"We can do better and maintain our position at the top of the table."
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