The Red Devils' 1-1 draw with Southampton on Saturday left them with just 11 points from their opening eight games - the club's worst start to season for 24 years.
"It is not easy reading now," Carrick told reporters. "Looking at the table as it is now is not something we are used to.
"It is frustrating because things are not going the way we want. But as players we have to stand up, take responsibility and get better.
"We just have to keep believing. We are still confident. Everything is in place but for some reason, at the moment, we are not quite clicking and not quite firing."
United face Real Sociedad in the Champions League at Old Trafford on Wednesday.