Gael Clichy says Manchester City must step up a gear and rediscover the form that led to them winning the Premier League last season.
The defending champions are second in the table but six points adrift of leaders Manchester United, who beat them 3-2 in a heated derby at the Etihad last weekend.
Although that defeat was City's first of the season, and their first at home for almost two years, they have largely failed to produce the sort of performances that led them to the title and have suffered a dismal campaign in the Champions League.
Defender Clichy told City's official website: "For me, the problem this year is that we are not playing as well as a unit as we did last year, and that's what we have to work on.
"I am very confident, though, because we have the quality. I am sure we are going to be there at the end of the season. I personally believe we have a mission, and its aim is to become champions again.
"The feeling within the team is great at the moment, and I hope that the fans are behind us because we will need them."
He said he felt City could take positives from the United game - in which they were 2-0 down but came back to 2-2 before succumbing to a late Robin van Persie strike - and move on from losing their long unbeaten home record.
"We hadn't lost a game for a long time at the Etihad, but it's done now and the only thing we can do is focus on the positive things that happened during that game," he added.
"We went 2-0 down and again we showed great team spirit in getting it back to 2-2. Apart from the last 20 minutes of the first half, I don't think they were on top of us.
"When you lose a game in the last minute it's always difficult, but we know what we did well and what we didn't do so well and we have to try to avoid those bad points."
City travel to Newcastle on Saturday - where they took a giant step towards last season's title with a 2-0 win - to face a Magpies side struggling for form.
Alan Pardew's side lost 2-1 to Fulham on Monday night to continue their recent troubling run of form, but Clichy warned that City would face a difficult task at St James'.
He said: "Three points against Newcastle away would be a great result and hopefully help us to catch up with United.
"It's a difficult place to go, and even more so because I think they've only won one of the last 10 games or something like that, so they will want to do something against the champions."
Information from the Press Association was used in this report