Pellegrini: We must be worried

Rolando Aarons and Moussa Sissoko struck as Newcastle claimed a shock 2-0 win against the holders in their fourth-round tie.

To compound matters as manager Manuel Pellegrini's decision to field a strong side backfired, in-form playmaker David Silva also limped off with a knee injury.

Silva could now be doubtful for Sunday's eagerly-anticipated visit of Manchester United in the Barclays Premier League. Midfielder Yaya Toure will also be assessed after being withdrawn as a precaution with a groin problem.

It has been a difficult past week for City with this latest result coming after a disappointing Champions League draw at CSKA Moscow and Saturday's unexpected Barclays Premier League loss at West Ham.

They must now rouse themselves for two more crucial games over the next seven days, with the United clash quickly followed by a home meeting with CSKA.

A continuation of the current run of form would raise questions over Pellegrini's stewardship of the side and the Chilean did admit he was concerned about form.

He said: "My feeling is that we are not playing well. We are in a difficult moment with a lack of trust.

"We are conceding too (many) easy goals and we are not scoring the chances we have to score. That's the feeling at this moment.

"It's a lack of confidence that we must address as soon as possible because we need to continue to be involved in the other competitions.

"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. It's not normal to see this team playing the way we are now."

City were rocked in the sixth minute as Ryan Taylor, returning to the Newcastle side after a two-year injury absence, robbed Fernandinho to set up the opener for the pacy Aarons.

City went close to replying, not least when Fabricio Coloccini hit his own post, but the hosts lacked intensity despite prolonged possession.

Newcastle seemed to be denied a blatant penalty in the second half when Gabriel Obertan appeared to be clipped by Aleksandar Kolarov, but substitute Sissoko soon rendered that academic with a great run and finish.

They will now face Tottenham in the quarter-finals and, after a dismal start to the season, they are enjoying a mini-revival and pressure on manager Alan Pardew could be easing.

Pardew said: "We believed we could win and that was shown out there on the pitch.

"It is a difficult place to come and we have not beaten them under my tenure. I don't think we have had the complete rub of the green (against them) and tonight we did, but it was an outstanding display."

Pardew also hailed the display of Taylor, who suffered cruciate ligament damage in August 2012.

He said: "He was outstanding and he is a beacon of light in professional football.

"We are delighted we have been able to give him a platform but he had 10 good players around him and we couldn't have asked for more."