Chelsea boss Thomas Tuchel admits the number of mistakes made by his players is affecting their confidence amid suggestions that his side could be dragged into a top-four battle.
The Blues' miserable run of form continued on Wednesday when they were beaten 4-2 by Arsenal at Stamford Bridge.
That result means that both the fifth-placed Gunners and fourth-placed Tottenham are five points behind Chelsea in third, though they have both played a game more than their west London foes.
Speaking to the media ahead of Sunday's clash with West Ham, Tuchel admitted the sheer volume of errors his players were making is a concern, and revealed he is never comfortable in the Premier League - a viewpoint that has to be shared across the board.
"I'm worried about the number of mistakes," Tuchel said. "In the year 2022, we already had eight big mistakes that led to goals. This is very untypical, very unusual.
"It costs us a lot. Not only a goal, it costs you self-confidence and belief in what you are doing.
"'It's a bit fragile at the moment," Tuchel added, referencing mistakes made by Edouard Mendy and Andreas Christensen in recent games. "Edou knows he can do better and normally does. Andreas knows it's the right decision to play the ball back. It's not that we take crazy risks. So it's hard to analyse.
"I never feel secure in the Premier League. Nobody should. Feeling secure does not keep you on the edge. Feeling secure is very close to being lazy or not fully alert.
Listen now to 90min's brand new podcast, Talking Transfers, with Scott Saunders & Graeme Bailey. Toby Cudworth joins the show this week to discuss contract situations at West Ham, while there are updates on Man City's pursuit of Erling Haaland and Chelsea's plans for Romelu Lukaku.
"Maybe it comes back to me because I should push them and make them alert. It's human to be tired, human to be more alert in a knockout game than normal matches," he continued. "Sometimes it's also good, the foundation to play 60 games. At Mainz with one game a week, every game was like a cup final and the players were drained until Tuesday.
"At Dortmund, players gave everything physically on a normal match but mentally it was not the same stress level. It's OK to feel less tension in front of a normal home match in the Premier League than if you go to the Bernabeu.
"It is maybe less tension, excitement and pressure. But it cannot lead to being less alert or having less investment. This can never happen. We cannot run more or do more sprints and more effort than against Madrid or Brentford. There were no doubts about it as we had the physical data.
"It's a little bit like this but not in the same way against Arsenal. That's why it's tough to really understand the reasons why."