Substitute Papiss Cisse struck twice as Newcastle United secured a 2-1 win to end Chelsea's 23-match unbeaten run in all competitions and inflict their first Barclays Premier League defeat of the season.
The Senegal international scored four minutes after coming on in the second half before adding what proved to be a decisive second goal with 12 minutes to play, ensuring Jose Mourinho has still never masterminded a league win at St James' Park.
Chelsea dominated the first half but failed to find a way through, with Willian and Cesc Fabregas both passing up presentable chances.
They were made to pay after 57 minutes, as Cisse netted his sixth BPL goal of the season by tapping in Sammy Ameobi's cross.
Cisse then doubled Newcastle's advantage, and although Didier Drogba pulled a goal back after Steven Taylor had been sent off for a second bookable offence, for the second time in the space of a week Chelsea dropped points in the north-east.
Defeat enables Manchester City to close the gap to just three points if they beat Everton later on Saturday.
Newcastle were able to celebrate a shock victory in which goalkeeper Jak Alnwick made some vital saves after coming on to make his debut at half-time following an injury to Rob Elliot.
Alan Pardew rang the changes after Newcastle's draw at Burnley on Tuesday, with Fabricio Coloccini and Remy Cabella two of five players coming in.
Chelsea welcomed back leading scorer Diego Costa from suspension at the expense of Drogba, while John Obi Mikel replaced the suspended Nemanja Matic in midfield.
The visitors dominated possession in the first half and had their first sight of goal after 10 minutes, when Willian fired narrowly wide of Elliot's goal after good work from Costa and Eden Hazard.
Chances continued to come for Chelsea but Willian again missed with a curling effort 18 minutes in, before Fabregas saw a low shot deflected wide.
Having soaked up plenty of pressure, Newcastle eventually began to pose more of an attacking threat and Thibaut Courtois had be alert to deny Jack Colback in the 31st minute, the midfielder collecting an Ayoze Perez pass inside the penalty area only to be denied by the Belgium goalkeeper.
Newcastle's goalkeeping problems worsened at half-time as Elliot, in for the injured Tim Krul, limped off and was replaced by 21-year-old Alnwick.
The debutant commanded his area well and having weathered another spell of Chelsea pressure, Newcastle opened the scoring.
Ameobi made good ground down the left, Cahill failed to deal with his low cross and Cisse had the simple job of tapping home from close range.
Mourinho introduced Andre Schurrle and Drogba from the bench and Chelsea began to lay siege on the Newcastle goal.
Valiant defending from Coloccini and Taylor denied Costa on the turn, and Hazard saw a low shot hit the post.
Newcastle then punished the leaders on the counter attack as Colback found Moussa Sissoko, who was unable to finish but when the ball rolled to Cisse the striker made no mistake.
Taylor was then dismissed for a second bookable offence after committing a foul on Schurrle and Drogba headed in Fabregas’s 83rd-minute free-kick moments later, setting up a tense finale.
Alnwick came to Newcastle's rescue in the closing minutes with saves to deny Costa and Filipe Luis and Newcastle held on for all three points.
Newcastle manager Alan Pardew: "That wasn't about substitutions. It was about character and discipline against the best team in Europe at the moment.
"At the start we stood off them, but we stuck at it and were always a threat.
"For us it's a special day and it's special day for Jak [Alnwick].
"At the end there were chances where we had two players blocking it. It was a real team effort. We're in it together, we had a tactical plan and it worked quite well. I am absolutely delighted for our fans, and it makes it more interesting for everyone else.
"They had chances, but you have to ride your luck. They'll take some stopping but today was our day."
Chelsea manager Jose Mourinho: "[I have] no complaints. [We were] unlucky, we had lots of chances to score in the first [half but] we didn't [take them].
"In the second [half] we had chances, but they defended [well], and the first time they go there [Chelsea's penalty box] they scored a goal.
"Then they get everyone behind the ball against a team that tried everything until the last second. We wanted to play more foot but it wasn't possible, no complaints.
"We didn't deserve this, but it is the result we had, we have to accept it and move on."
|13 Dec 2014||v Arsenal (A)|
|21 Dec 2014||v Sunderland (H)|
|26 Dec 2014||v Man Utd (A)|
|28 Dec 2014||v Everton (H)|
|01 Jan 2015||v Burnley (H)|
|10 Jan 2015||v Chelsea (A)|