Since his deadline day move from Liverpool the team has lost against his former club and endured a scoreless draw at Fulham.
The club's Italian coach belives that the 26-year-old needs time to adapt his game at Stamford Bridge and that the recent run of games have not been a consequence of the strikers arrival.
The former Milan boss told reporters: "It is not the fault of Fernando, obviously. I think that he needs to have time.
"In my opinion, he played well for 60 minutes against Fulham. He had two or three opportunities.
"He didn't score but he will score, obviously.
"He needs to have time, but playing, to improve his combination with the other players. It will take time playing with us."
Meanwhile, with the former Athletico Madrid man's ineligibility to play in this weekend's FA Cup tie against Everton, Didier Drogba rerturns to the starting line-up after beginging the game at Craven Cottage on the bench, and Ancelotti claims that the Ivorian's spirits are still high at the club.
The Italian added: "Didier had a very good reaction during the week, he trained well without problem, with motivation. He wants to play a good game tomorrow."