Jermain Defoe capped off a fine comeback after a much-improved second-half showing to move out of the relegation zone, while John Terry could have played his last game for Chelsea.
Sunderland completed a fine second-half comeback against Chelsea and give a big boost to their survival hopes, while John Terry was given a late red card to rule him out for the rest of the season.
Diego Costa opened the scoring, latching on to a deflected Gary Cahill pass, only for the Black Cats to fight back and equalise through Wahbi Khazri’s fine edge-of-the-box volley.
As Sam Allardyce’s men looked to hold Chelsea until the break, Nemanja Matic stroked the ball between Vito Mannone’s legs with the last kick of the half reinstate the visitors’ lead.
Costa should have settled the game just before the hour mark when one on one with Mannone but could not beat the Sunderland goalkeeper and the hosts soon mounted a comeback.
Fabio Borini equalised 10 minutes later, his snap shot from inside the area diverted in off John Terry, before Jermain Defoe yet again popped up with a crucial goal to seal a huge three points in the relegation battle.
To pile on the misery for the visitors, Terry was sent off deep into injury time to hand him a two-game ban, for his second red card of the season, in what could mark his final act as Chelsea captain.