Manchester City manager Manuel Pellegrini says he is "worried" by his side's form going into Sunday's Premier League derby against Manchester United.
Holders City were knocked out of the League Cup by Newcastle on Wednesday, having drawn at CSKA Moscow and lost at West Ham in their previous two games.
Pellegrini spoke of a "lack of trust and confidence" among his players.
"We must address this as soon as possible," the Chilean said. "We will try to react as soon as we can."
The 2-0 defeat by a youthful Newcastle side at Etihad Stadium capped a difficult week for Pellegrini and the Premier League champions.
Pellegrini made seven changes from Saturday's 2-1 league defeat by West Ham but still named a strong side led by Ivory Coast midfielder Yaya Toure and containing 10 internationals.
But they produced a lacklustre display as goals from Rolando Aarons and Moussa Sissoko put Newcastle into the quarter-finals.
City, who are third in the table, entertain a United team that are four points and five places behind their neighbours in the table.
"My feeling is that we are not playing well. We are in a difficult moment with a lack of trust," Pellegrini said.
"We are conceding too (many) easy goals and we are not scoring the chances we have to score.
"Of course we must be worried - we didn't win the three games we played this week. We must be worried about that but we must find a solution and we must address it.
"We will see with the players which is the way to try and recover that confidence because it's not normal to see this team playing the way we are now,."
Forward David Silva was substituted after only nine minutes against Newcastle, while Toure was replaced after an hour.
"David has problem in his knee. We will see tomorrow how big is it," Pellegrini said.
"Yaya was with some problem in his groin, but I think that's nothing important."