Chelsea captain John Terry says the club's recent form is "unacceptable" as their hopes of winning the league recede.
Chelsea had been widely expected to retain the title after making a blistering start to the new season, but they currently sit fifth in the table as they have had to cope with injuries to key players and the departure of assistant manager Ray Wilkins.
Terry insists Chelsea still believe they can be serious challengers for the Premier League, Champions League and FA Cup, but he knows a substantial improvement is required.
"Our recent performances have not been good enough," he said in the Daily Star. "We're not playing at the level we can and we're slipping further behind the leaders with every point we drop.
"That's unacceptable for a club like this, where we expect to win every game, and now we have to start to put things right. This squad should be challenging at the top of the league, winning games and pushing hard in every competition.
"That remains our aim, even if we have gone off course recently but, before we start thinking about silverware, we have to concentrate on starting to win games again."