Chelsea scored an injury-time goal as they came from a goal down to win 2-1 at Cardiff and ease the pressure on manager Maurizio Sarri.
The Londoners -- who started with Eden Hazard, N'Golo Kante and Callum Hudson-Odoi on the bench -- equalised in controversial fashion six minutes from time when Cesar Azpilicueta, clearly offside, headed home when a corner was flicked on.
And they won the game through Ruben Loftus-Cheek, who headed home in the first of seven added minutes to put them level on points with fifth-placed Arsenal.
A superb Victor Camarasa goal in the opening seconds of the second half had given Cardiff the lead, with the home side further aggrieved when Antonio Rudiger was shown only a yellow for a last-man foul on Kenneth Zohore in the closing minutes.
Chelsea had claims for a penalty in the opening moments, Aron Gunnarsson appearing to foul Rudiger at a corner, but nothing was given.
Pedro was within a whisker of putting the visitors in front after 11 minutes, finding space 25 yards out and whipping a shot off the top of the bar.
A couple of minutes later Cardiff also came close, Josh Murphy curling his angled strike narrowly wide.
Both sides were struggling to produce anything in a drab first half, Jorginho snuffing out a Murphy run with a clumsy challenge that saw him booked.
Alonso ballooned an effort high after neat build-up play, and Willian bent a free kick off target from a promising position 25 yards out.
In the opening seconds of the second half, Cardiff took the lead with a goal whose quality was out of keeping with what had gone before, Gunnarsson and Harry Arter combining for Camarasa to send a superb cushioned finish beyond Kepa.
With Chelsea ragged, Barkley dragged a low effort well wide and after 53 minutes Sarri had seen enough, introducing Hazard for Pedro. The Belgium international swiftly drew a foul from Arter, with the Cardiff man booked.
Hoilett bent an ambitious effort wide from range as Cardiff looked the more dangerous side, and Azpilicueta was booked for a foul on Niasse.
Sarri made another switch after 64 minutes, Jorginho off and Ruben Loftus-Cheek on, and they almost found a leveller when Gonzalo Higuain fed Loftus-Cheek and the ball fell to Hazard who was unable to get a shot away inside the area.
As the game approached its final 15 minutes, Willian found space but pulled a low strike past the post, and Sarri made his final change as Olivier Giroud came on for the ineffective Higuain.
Cardiff replaced Arter with Ralls but, with time running out, their hopes of a crucial win in the battle for survival were to disappear in cruel fashion.