Anwar El Ghazi cancelled out Olivier Giroud's header as Aston Villa stole a 1-1 draw at Stamford Bridge to stay above Chelsea in the Premier League table.
El Ghazi tapped home at the far post with the Blues frustrated neither the officials nor Villa had stopped play, with Andreas Christensen out of commission after a heavy challenge with Jack Grealish.
Giroud had nodded Chelsea into a 1-0 half-time lead, the France striker gleefully posting his ninth Blues goal of the campaign in all competitions.
But Frank Lampard’s men could not get back to winning ways after their 3-1 loss at Arsenal on St Stephen's Day, to be left instead with just one victory in their last five league matches.
Villa by contrast extended their unbeaten run to five matches, to sit fifth in the table and hold off Chelsea in sixth.
Chelsea boss Lampard made six changes from the St Stephen's Day defeat at Arsenal, but will have been frustrated not to receive the upswing in performance he had demanded.
Villa's neat build-up play and compact work off the ball kept Chelsea pegged back regularly throughout a cagey opening half hour.
Grealish drew a good save from Edouard Mendy with an early tester, before the Villa captain unwittingly teed up Christian Pulisic.
Grealish's loose ball gifted Pulisic a run in on goal, and the USA forward should have found the back of the net, not the side netting.
Matty Cash blazed over after Mendy was unable to reach a cross as Villa threatened again.
Pulisic then hooked over from point-blank range when it appeared easier to score, and as time ticked by Chelsea were staring at a half-time stalemate.
But just when Villa were gearing up to be reasonably satisfied with their work, Chelsea finally strung together a move of purpose and incision.
The first true flowing attack from the Blues yielded the breakthrough, as Chilwell delivered the telling cross – and Giroud applied the deadly finish.
France hitman Giroud had been involved in the build-up, flicking a back heel to Pulisic, before ghosting into the box, losing his marker and converting in style.
Villa snatched an equaliser shortly after the break to halt Chelsea's momentum, though the legitimacy of the goal would be long debated.
El Ghazi tapped home at the far post but would arguably not have had the space to do so had Grealish been censured for his tackle on Christensen in the build-up.
The Denmark defender stepped too far out of defence, but was left on the ground after a robust challenge from Grealish.
Villa chose not to put the ball out of play, eventually taking full advantage to level at 1-1.
Chelsea rallied straight away, with a neat move to culminate in an 18-yard drive from N’Golo Kante.
The France midfielder had acres of space and plenty of time, and while he did hit the target, in truth he should have scored.
John McGinn rattled the crossbar with a 25-yard pile driver as the game started to break up, before Chelsea rolled out their replacements in a bid for a winner.
Timo Werner and Kai Havertz were pitched into battle, with Chelsea desperate for the victory.
Pulisic saw a rasping effort tipped over by Emiliano Martinez, but Villa substitute Jacob Ramsey could have stolen it, whipping just wide with Mendy beaten.