In an extraordinary reversal of fortunes, the teams are preparing for Monday's meeting at Leicester with the home side top and Jose Mourinho's champions stuck in 14th place.
In an added irony, the man who has taken Leicester to the head of the table, Italian Claudio Ranieri, was sacked by Chelsea in 2004 to facilitate Mourinho's arrival.
"I said a couple of weeks ago, I didn't believe they can be champions," the Portuguese coach told a news conference on Friday. "Maybe I have to think twice before I say that again.
"One thing is to be top of the league in September. Another thing is to be top in December."
November's manager of the month, Ranieri, he said, should be acclaimed as "manager of the half-term" as the season approaches its midway stage with the traditionally busy Christmas period.
Mourinho was keen to point out that Leicester's rise and his own team's demise are two separate things.
"They are where they are because they are doing magnificent and we are where we are because we are doing bad," he said.
Mourinho added that Chelsea's poor results have made him "embarrassed" and unsure how to respond when the Blues fans chant his name, as they have continued to do during the worst period of his managerial career.
Despite that, and a stunning home defeat by promoted Bournemouth last weekend, Mourinho believes Chelsea's win over Porto in midweek and their improved defensive record means they can still qualify for next season's Champions League.
"We can get a run of four or five wins in a row and we can finish fourth. Independent of the defeat against Bournemouth, I think the team is improving."
He cited a new "defensive stability", with one goal conceded in five games, compared to 12 in five earlier in the season.
Mourinho said Chelsea "need to score more goals". which he was confident would happen after a run of only one in four league games.
(Reporting by Steve Tongue; editing by Ken Ferris)
