John Obi Mikel admits Chelsea have lost their steel in the absence of John Terry, Frank Lampard and Michael Essien.
The Blues have lost three of their last four league games, surrendering their four-point lead at the top of the Premier League table in the process.
Carlo Ancelotti's boys remain top on goal difference but midfield grafter Mikel believes injuries to key players have softened their approach.
"We are short of physicality, short of players," Mikel told The Sun.
"We used to tend to push teams aside even when we were not playing well. It's kind of a struggle for us.
"When the season started everybody said that Chelsea would go unbeaten. We were playing very well, creating chances and scoring goals.
"We got used to the first-team players and now most of them are not there.
"Players like Lampard, Essien, JT have been injured, Alex doesn't play. No disrespect to those playing now but we are missing these players."
Terry and Lampard are edging closer to a return to the first team and could feature against Everton next weekend, but Essien is suspended for Sunday's visit to Newcastle.