Marcos Alonso's double helped the leaders brush aside the poor defending champions as Antonio Conte's side clinched a 3-0 win
Pedro added a third and the visitors exorcised any demons at the King Power Stadium following defeat which cost ex-boss Jose Mourinho his job during last season's dismal campaign
After that 2-1 win in December 2015 Leicester were on the way to a stunning title success but fast forward 13 months and defeat was their 10th of the season and they are five points above the relegation zone
Chelsea started the game four points clear having lost their 13-match winning league run with a 2-0 defeat at Tottenham but the focus was on the missing Costa after reports of a bust-up with boss Conte.
The striker did not travel with the rest of the squad and Chelsea had initially declined to comment on Friday's reports but before the game Conte said, via the club's Twitter account, the 28-year-old suffered a back injury on Tuesday
Costa, Chelsea's 14-goal top scorer, has been linked with a move to China and was replaced by Willian in the visitors' only change from their loss at Spurs two weeks ago
Eden Hazard started as the most advanced but the leaders' early opener came from an unlikely source.
Ahmed Musa had already threatened Thibaut Courtois but Chelsea quickly took control and were ahead four minutes later
Cesar Azpilicueta's delicious cross caused chaos in the Leicester defence before it fell to Hazard to tee up the unmarked Alonso to hammer in from six yards
There was little reaction from Leicester as Chelsea threatened a procession with the Foxes completing just 15 passes inside the opening quarter of an hour
The rotation of Chelsea's front three, Hazard, Willian and Pedro, caused the hosts issues, with Willian particularly impressive, and any threats were batted away by Gary Cahill and David Luiz as the subdued Foxes looked short of ideas
Without Riyad Mahrez, on African Nations Cup duty with Algeria, they lacked their main supply line to Jamie Vardy and Musa with the pair living off scraps
The only real alarm came after 36 minutes when Courtois palmed away Vardy's low cross but the visitors always held a degree of control
Yet they failed to add to their lead in the first half having failed to test Kasper Schmeichel since opening the scoring, although a neat free kick move ended with Pedro firing wide three minutes before the break
There was almost an air of resignation from Leicester since the early goal and a second for Chelsea finally arrived six minutes into the second half
Willian was fouled by Christian Fuchs and his right-wing free-kick was only half cleared to Alonso and the left-back's low 18-yard drive hit Wes Morgan to squirm past Schmeichel
It was the strike Chelsea deserved and they went hunting for more as Cahill's overhead kick was blocked before Alonso was inches away from a shock hat-trick when his ambitious first-time volley dropped wide
But Pedro wrapped up the points with 20 minutes left as Chelsea underlined their superiority and the gulf between the two sides
His flick found Willian and, when the midfielder's cross looped off Schmeichel, Pedro rose to nod into an empty net
Source : PA
Source: PA