A Seydou Doumbia brace secured the Russians’ first victory on English soil while both Fernandinho and Yaya Toure received their marching orders, leaving the reigning Premier League champions languishing in bottom-place in Group E with just two points.
"It's a crisis of confidence, of course, but we must find out why," he told Sky Sports. "We will talk to the players every day and try to win again.
"It's difficult to understand why we played so bad. From the beginning we are so nervous and we lose so many passes. We gave them the two goals and really we didn't play.
"It's difficult to know why you have so low performance from important players. The way we tried to play, we are not changing anything from what we've done in other games. It's a strange moment to understand why.
"In the last two weeks we are not playing the way we normally do. I don't understand why but we must find a reason.”
City have two tough matches against Roma and Bayern Munich left in their group, yet their Chilean boss insists they can still progress to the Last 16 of the competition.
“You never must think you're out when mathematics say you are in,” he said.
"Not only for Champions League because we have Premier League this Saturday against QPR - we must try to return to our normal performance."