Chelsea manager Jose Mourinho has questioned the "unstable attitude" of some of his players during the club's poor start to the season.
Mourinho said his side, who won the Premier League last season but are 14th after seven games of the current campaign, lack "serial champions".
Chelsea visit Mourinho's former club Porto in the Champions League on Tuesday.
"Clearly it's an attitude perspective of some individuals," he said.
"And when you have individuals with that unstable attitude in terms of motivation, desire and commitment you will pay."
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Chelsea finished eight points ahead of runners-up Manchester City in the Premier League last season but have failed to win five of their first seven league games this term.
However, they did beat Maccabi Tel Aviv 4-0 in their opening Champions League group game earlier this month.
Mourinho claimed only defenders John Terry, 34, Branislav Ivanovic, 31, and 28-year-old midfielder John Obi Mikel have won multiple titles - and that no-one's place is safe if the club's poor form continues.
"There are two sorts of champions," added the 52-year-old Portuguese.
"There are champions who win something - and there are lots of them - but there are the other champions who during their career win one, two, three, four, five, 10 or 20 titles.
"We have 25 champions from last year - but serial champions in this squad, how many do we have?
|According to Opta's rating system, only two of Chelsea's players make the Premier League's top 50 this season|
|1. Riyad Mahrez||Leicester City||563||230|
|2. Jamie Vardy||Leicester City||622||183|
|3. Romelu Lukaku||Everton||606||180|
|4. Dimitri Payet||West Ham United||628||179|
|5. Yaya Toure||Manchester City||586||171|
|21. Eden Hazard||Chelsea||630||128|
|31. Cesc Fabregas||Chelsea||599||118|
"I can be five or 10 years without winning a title, but I will still be a serial champion in my approach and my attitude. This is the problem we have at this moment."
Mourinho has left former England captain Terry out for the past two Premier League games, while Ivanovic and midfielder Cesc Fabregas have been criticised.
Terry has started only the League Cup win at Walsall since a 3-1 loss at Everton on 12 September.
In 2006, during his first spell in charge at Stamford Bridge, Mourinho described eight of his first-team players - including Terry, Ashley Cole, Frank Lampard and Didier Drogba - as "untouchable" because of their form.
"Only consistency can give you that status," said Mourinho. "Football is about today. At this moment I don't have untouchables.
"To be a winner you don't need to win all the time, but you must have a strong mentality every game, every day."
Mourinho will have striker Diego Costa available in Porto as his three-match ban over an incident involving Arsenal's Laurent Koscielny does not apply to European games.
Asked if he needed 11 Costas on the pitch, Mourinho said: "We would lose every game, because the desire to suspend him is so big that we wouldn't have players to start the game.
"I'm happy to have only one and let him play until they decide to suspend him again."
Porto drew their opening Group G match 2-2 at Dynamo Kiev.