Chelsea failed to make use of the chance to close the gap on the second placed Manchester City by conceding a 3-2 defeat to Newcastle United at St. James' Park on Saturday.
Moussa Sissoko's double goal on his home debut crashed the hopes of Rafa Benitez's men.
Jonas Gutierrez opened the account for Newcastle in the 41st minute by heading the ball into Petr Cech's net from Davide Santon's cross.
The European champions fought back in the second half with a long-range goal from Frank Lampard in the 55th minute, his 10th goal of the season. Juan Mata put Chelsea in the lead in the 61st minute by curling the ball into Tim Krul's net from Fernando Torres' pass.
However, Newcastle's new signing Sissoko found an equiliser in the 68th minute after Cech sent Yoan Gouffran's shot straight to him. The France midfielder once again scored the winner for Newcastle in the 90th minute when it seemed the game would end in a draw.
Chelsea did get a few chances to walk away with three points, and one of them was Fabio Coloccini's inside the box challenge on its striker Demba Ba, which forced him to leave the grounds with blood pouring from his face. But overall, Newcastle played better on the day, not letting the Blues play their usual game.
Chelsea ended the week with a dismal performance, drawing 2-2 with relegation-threatened Reading on Wednesday. It is placed third in the Premier League table with 47 points from 25 games, behind Manchester United (59) and Manchester City (52) from 24 games each.
Newcastle is now on the verge of being cleared from the relegation zone following Saturday's win against Chelsea.