Gary Neville has warned Frank Lampard that he must solve Chelsea's problems quickly.
Pressure is building on Lampard following a run of four defeats in six matches.
Sunday's 3-1 loss to Manchester City has left the Blues eighth in the Premier League table - seven points behind leaders Liverpool, who have a game in hand.
Lampard guided Chelsea to a top-four finish last season, having had to work under a transfer embargo at one stage.
But with more than £200million spent on new players over the summer, the expectations have risen.
Neville says the recent dip in form is a major concern.
"I think they (Chelsea) will be worried," the former Manchester United defender said on his latest Sky Sports podcast.
"Frank will be worried. He'll want to get back on track quickly.
"The performances have been poor these last few weeks.
"I've watched them and they've not been fluid, they look like they've been struggling.
"I thought having (Hakim) Ziyech back was a bonus, and (Christian) Pulisic on the left, we know how good he was coming out of lockdown at the end of last season.
"And with (Timo) Werner up front, I thought they could really cause City problems with their movement, but they never really got a foothold in the game, those three. They looked weak.
"The midfield didn't get a grip of the game and then, at the back, they got pulled apart. The two full-backs really struggled in the first half."
Neville added: "It's now getting to that point where I thought Frank had settled his team down after a difficult start to the season.
"But now I'm thinking again does he know his best team? And he seems to have gone back to square one.
"But he's going to have to work it out quickly, because he'll be concerned by what he's seen - (against Man City) I think less so, second half I think he'll be happy, getting that goal at the end.
"But he's got to sort this out quickly here, because ultimately it's a club that needs success, with the money they've spent.
"And at this moment, it's a problem for him. The performances are a struggle. They don't look happy out on the pitch as a team.
"I don't mean happy as in the body language, I mean happy in terms of playing with each other and the combinations.
"They don't look like they've got the right rhythm in the game."
