Eight second half minutes transformed Chelsea from chumps into champions as substitute Oliver Giroud smashed home a brace as the Blues came from 2-0 down to Southampton to record a sensational 3-2 victory at St Mary’s Stadium.
The Blues looked dead and buried after the relegation-haunted home side doubled their lead on the hour mark from Jan Bednarek after Dusan Tadic opened the scoring in the first half.
Antonio Conte immediately brought on Giroud for lifeless Alvaro Morata and the impact was imidiate.
A diving header and a thumping left-footer by the Frenchman were sandwiched between a Eden Hazard strike and the comeback was complete.
The first half was a horror show from the Londoners, the second-half showed what they could do, when they put their collective minds to it.
A tentative start by both sides with the Saints edging the early exchanges. Two excellent byline crosses from the left, failing to find a home side striker, leaving Marcos Alonso to hack the danger ball clear.
A brilliant free kick by Willian on 19 minutes, from the left, zipped into the six-yard box. Alonso and Alvaro Morata were both close to getting a touch on it, but goalkeeper Alex McCarthy sniffled the ball.
But up swept the Saints and Ryan Bertrand showed a clean pair of to Cesar Azpilicueta. he raced onto the byline and cut the ball back to in-running Dusan Tadic, who cooly slotted home, from six-yards, ahead of a late challenge from Gary Cahill to put the home side ahead on 21 minutes.
Morata almost levelled on 27 minutes. A fine counter-attack and possession by the Blues resulted in David Zappacosta putting in a deft clipped cross into the centre of the saints six-yard box. However the Spain striker was a tad late to the ball and he overstretched and headed over the crossbar.
Two minutes, a deep Willian corner to the far post almost caught McCarthey out as the ball seemingly arrowed into the net, but he managed to get a left hand to the ball and scoop it away from danger at the last moment.
A diving header by Andreas Christensen, went well wide from an cute, angled pass from Hazard was the last action of a disappointing first half as far as Chelsea were concerned.
There were no changes by either side at half-time
Southampton should have doubled their lead on 50 minutes when a long ball found Shane Long, Mahon out sprinted Christensen and raced in on goal.
The Dane recovered enough to push the striker over. But rather than give a penalty and send the defender off, referee Mike Dean played on, allowing Long to get up, and in one quick movement turn and shoot. But the ball defected off Christensen for a corner.
At the other end, the Blues had a couple of chances. McCarthey, on hand to get to Willian and hazard’s efforts.
Goal number two was so simple. A deep free-kick by Oriol Romeu and Jan Bednarek was at the far post, unchallenged and he rammed the ball home.
Antonio Conte instantly replaced Morata and Zappacosta, bringing on Olivier Giroud and Pedro.
On 70 minutes, the Blues struck. Again the simple curling ball from the byline, this time by Morata, was met full on the head by Giroud, who directed the ball low and wide of McCarthy to reduce the deficit.
The comeback was complete five minutes later, after a sustained period of pressure by the Blues, again the clipped ball from the left - by Willian, saw the ball fall to their left peg of Hazard who smashed it high into the back of the Saints net from eight yards out.
Three minutes later and incredibly Chelsea took the lead. Willian to Hazard, and then the Belgian dinked the ball into the penalty area.
the ball was knocked back to the edge of the area and Giroud was at hand the lash the ball home with a daisy-cutting left-footer to secure all three points.
Next up is a trip to Burnley on Thursday before a return date with Southampton, at Wembley on Sunday in the Fa Cup semi-final.
Chelsea: Courtois; Azpilicueta, Christensen, Cahill; Zappacosta, Kante, Fabregas, Alonso; Willian, Morata, Hazard.
Subs: Caballero, Moses, Emerson, Bakayoko, Barkley, Pedro, Giroud.
Saints: McCarthy, Cédric, Bednarek, Hoedt, Yoshida, Bertrand (c), Romeu, Ward-Prowse, Tadić, Højbjerg, Long.
Forster, Austin, lemons, Boufal, gabbiadini, McQueen, Sims
Referee: Mike Dean