A double strike by Jimmy-Floyd Hasselbaink and late goals from Adrian Mutu and Celestine Babayaro rekindled Chelsea's title challenge but pushed Leicester City deeper into the relegation mire.
Chelsea manager Claudio Ranieri opted to make six changes to the side beaten at home by Liverpool.
In came Mario Melchiot, Marcel Desailly, Babayaro, Jesper Gronkjaer, Eidur Gudjohnsen and Hasselbaink.
Axed were Glen Johnson, William Gallas, Wayne Bridge, Geremi, Mutu and Hernan Crespo.
An Achilles problem meant Muzzy Izzet was a surprise late omission with Lilian Nalis filling the midfield void.
The Londoners threatened first on three minutes when Hasselbaink was put clear by Gudjohnsen. He was driven wide by Ian Walker who then stood his ground to block the Dutchman's eventual shot.
Moments later, only a late intervention by Steve Howey denied Hasselbaink a clear sight of goal.
Chelsea were looking lively and it was no surprise when they sliced open the left rearguard to take a deserved lead on 11 minutes.
Melchiot played in Joe Cole who took the ball to the byline before crossing to the near post where Hasselbaink got in front of Nikos Dabizas to cleverly turn the ball in from close range.
It was all Chelsea as Walker did well to parry Hasselbaink's angled drive.
City had to wait until the 39th minute to threaten when Marcus Bent got in front of Melchiot to head a Nalis corner narrowly over.
But Leicester found themselves two down a couple of minutes before the break, although there was a huge slice of luck about it when Hasselbaink's 25-yard free-kick took a wicked deflection off Dabizas, completely wrong-footing the keeper.
Walker came to City's rescue soon after the re-start, diving to cut out a Frank Lampard cross with Gudjohnsen ready to pounce.
City began to enjoy more possession as Chelsea eased off, but struggled to make an impression, despite the introduction of Les Ferdinand and wide man Paul Brooker.
Callum Davidson finally put Carlo Cudicini to the test with 15 minutes remaining with a well struck 20-yard drive that the flying keeper palmed over the bar.
Leicester went close again, this time John Terry clearing a James Scowcroft header from Marcus Stewart's free-kick off the line.
After Paul Dickov had screwed a good chance wide, Chelsea finally killed off any hope of a Leicester revival with three minutes remaining when substitute Mutu picked up a Babayaro pass and cut inside before unleashing a 22-yard drive that left Walker with no chance.
And then in time added on Babayaro seized on a mistake by Brooker to crack an angled 16-yard drive inside Walker's near post.
Afterwards Hasselbaink said: "Everyone was up for this today. We knew we had everything to prove and it was a good performance with us showing what Chelsea are all about.
"We're very much back in the title race. Now we have to believe we can win every match. Hopefully this will also mean that our bad spell is over." Micky Adams, the Leicester manager, said afterwards: "I was disappointed with our first-half performance. Their second goal just before half-time was a killer.
"But we picked up in the second half, Cudicini made a great save from Davidson and then they went on to get two late goals.
"But it was a story of two teams. They've spent an awful lot of money and we just couldn't live with them today."