Claudio Ranieri fears Leeds United may be about to find their form and keep their manager Terry Venables in a job.
Venables has been under pressure virtually all season but the 2-1 victory over Sunderland on Boxing Day extended their unbeaten run to three games.
Ranieri, whose team are pushing the leaders Arsenal hard in the title race, knows Chelsea cannot underestimate Leeds, even if they have not won at home in the Premiership since September 14 - when they beat another contender, Manchester United.
On the eve of Chelsea's visit to Elland Road Ranieri said: "Always I am careful when you play teams like this because sooner or later they will explode. I hope it's not against us. It will be hard. I remember the games against them very well. They are very aggressive.
"I don't understand how it's possible for them to be so low in the table. I can't believe what has happened. More or less they have the same players as a year ago, when they were top. I am sure they will come back."
Ranieri believes that Venables, who spent eight years at Chelsea as a player, is capable of turning things around.
"I don't know him very well, I only know his reputation. [He] is a great manager, tremendous," Ranieri added.
"I don't remember being in a position like Venables but you have to carry on working and doing what you believe."
Venables, returning the compliment, believes Ranieri's side are Arsenal's main rivals.
"I'm not surprised how well Chelsea have done, not at all," said Venables. "They seem to have had roughly the same players week in, week out; that makes a difference. Are they serious title challengers? Yes.
"They are certainly looking consistent and that is why they are where they are. A couple of years ago I thought they were different when teams got stuck into them, but not now.
"The difference is that Chelsea have their top-class players playing well. It couldn't be harder for us to get a home win, that's for sure."
Ranieri had a stuttering start as Chelsea's coach but is now seeing his team push for honours; Venables can only hope he is given a similar chance.
"All credit to him," said Venables. "What he's done is very similar to what I'm trying to do here but he's in a much better position than I am."
Leeds are set to reward James Milner, the youngest scorer in Premiership history, with a lucrative new contract. The winger is ready to agree a deal worth almost £1,000 a week next Saturday, his 17th birthday.
