The Chelsea boss was left to rue Frank Lampard's late penalty miss as they let an early lead slip to concede their first league goals in six weeks but, although Ancelotti believes Cech was to blame for City's winner, he insists he still has full faith in the Czech Republic international.
"This season, over the whole campaign so far, Petr has done very, very well," he said. "I like him. He takes the responsibility and likes to come out and catch the ball in the box. But if you ask me about the free-kick on Saturday, he could have done better.
"If the keeper stays in the right position, by the post, and the opposition player puts the ball over the wall and in, we have to congratulate him. It was not like that at City. But even a good goalkeeper can make a mistake sometimes."
Chelsea face Cypriots APOEL Nicosia in the Champions League on Tuesday, and with his side already qualified for the knock-out stages, Ancelotti, whose side have now lost two games on the trot, is likely to hand French youngster Gael Kakuta his first start and rest skipper John Terry, Michael Ballack and Ashley Cole.