All hell broke lose 20 minutes from the end of the 1-1 draw with Burnley as first Nemaja Matic was sent off for retaliation to a career-threatening challenge by Ashley Barnes and then the Blues succumbed to an equaliser that has put a dent in their title ambitions.
Branislav Ivanovic opened the scoring for the league leaders on 14 minutes and the Blues should have gone on to rattle a cricket score. Instead, they failed to break down a plucky Burnley side and paid the price.
With 20 minutes on the clock Ashley Barnes scythed down Nemanja Matic with a horror challenge.
The Serbian got up and retaliated by pushing Barnes who collapsed to the floor.
Referee Martin Atkinson, who failed to spot the initial challenge, showed a red card to Matic.
Seconds later and Ben Mee headed home for the visitors from a corner.
A sedate opening five minutes was punctuated by a sublime cross from left-back Filipe Luis to in-running Juan Cuadrado. The speedy winger's powerful header was goal-bound but stopper Tom Heaton was equal to the effort.
A smart volley by Barnes a minute later, one well held by Thibaut Courtois, signalled Burnley's intent, of when they can get forward, they will shoot on sight.
But it was the Blues who struck first, on 14 minutes. Juan Cuadrado fought to regain possession of the ball on the byline on the right. He gave it to Eden Hazard who weaved through two defenders before cutting the ball back where Bransilav Ivanovic was well placed at the near post to slot the ball home between Heaton and the post. It was the Serbian's 31st goal in Blues colours and his sixth in total this season.
Ivanovic thought he should have had a penalty on 31 minutes when his pile driver appeared to hit the outstretched left hand of Michael Kightly, but referee Martin Atkinson chose to ignore the Chelsea appeals.
Atkinson's next significant decision was to wave away a shove on Diego Costa by skipper Jason Shackell, in the Burnley area that was as clear a penalty as the first one.
The first effort of the restart fell on 50 minutes to Barnes, and his angled half-volley from just inside the Chelsea area took a deflection, making Courtois's save, tipping the ball over his crossbar, even more remarkable.
The Blues carved out three excellent chances from the left in quick succession, each time thwarted by a combination of bad luck, last-ditch tackles and, in the case of Costa, sluggishness.
But it was Cuadrado who Jose Mourinho opted to replace on 62 minutes, Willian reinstated in the wide right berth.
Then all hell broke lose with 20 minutes to go. Barnes left his boot slide down the shin of Nemanja Matic who, after he got up, raced over to Barnes and shoved him to the ground. Atkinson showed a red card to the midfielder. Barnes, for his career-threatening, challenge received no punishment,.
Mourinho took off Oscar for defensive-minded Ramires to shore up the midfield.
A minute later, Courtois thwarted Barnes with a fine save that went for a corner, from the resultant kick, Ben Mee was on the spot to head the ball in past Courtois.
Mourinho was about to bring on Gary Cahill but decided not to. Once the goal went in, he changed his mind and brought on Didier Drogba for Luis.
However he could make no decisive difference.
Teams: Chelsea, Courtois, Ivanovic, Luis, Fabregas, Zouma, Oscar, Hazard, Costa, Matic, Cuadrado,Terry
Subs: Cech, Ramires, Drogba, Remy, Willian, Cahill, Azpilicueta
Burnley, Heaton, Tripper, Shackell, Mee, Ings, Kightly, Jones, Boyd, Barnes, Keane, Arfield
Subs, Gilks, Duff, Wallace, Vokes, Reid, Jutkiewicz, Ward.