After enjoying an impressive start to the season, Drogba has scored only two goals in his past nine games for Chelsea. While he did find the net in his past appearance away at Tottenham, the striker also failed to score an injury time penalty in the draw at White Hart Lane.
Drogba and Chelsea travel to Emirates Stadium on December 27 and the Ivorian boasts an impressive record against the Gunners, scoring four times against them in two appearances last season.
Ancelotti admits he has not seen the best of the striker who top scored in the Premier League with 29 goals last season, but hopes Drogba will rectify that next Monday.
"We need Drogba to come back to the performances he had last year and the goal against Tottenham was very good for his attitude," Ancelotti said. "I understand he has not been in a good condition. He had difficulty to play with malaria, he was tired, he was not 100% and he found it difficult to train.
"Now his condition is better. He had a good reaction after coming on as a substitute in the last game, this is the important thing and following the goal against Tottenham he will show us a different Drogba in the next game."