West Bromwich Albion moved into the Premier League's top four with a superb 2-1 win over a weakened Chelsea side at The Hawthorns.
Shane Long's early goal was cancelled out by Eden Hazard's deflected header six minutes before half-time.
But Peter Odemwingie converted a Long cross with a glancing header early in the second half and West Brom repelled a fierce Chelsea assault.
Boaz Myhill made several crucial saves from the wasteful Daniel Sturridge, and Chelsea boss Roberto Di Matteo was left to rue leaving numerous key players - including Juan Mata and Oscar - out of his starting line-up.
Di Matteo made four changes to the side that drew with Liverpool last weekend, clearly with an eye on Tuesday's crucial Champions League game away to Juventus.
Sturridge, Oriol Romeu and Victor Moses all made rare starts, while a formidable bench was graced by Mata, Oscar, Ashley Cole and Ramires among others.
Sturridge and Moses provided rather a ragged alternative to the sophisticated Mata and Oscar, and though both saw plenty of the ball they struggled to open West Brom up.
Increasingly, Sturridge looks like a man incapable of spotting a team-mate and he launched several optimistic and unsuccessful first-half shots.
Moses was equally wasteful late in the first half when Gary Cahill teed him up on the right side of the box.
The home side started stronger, with Youssouf Mulumbu and the excellent Claudio Yacob controlling the game in the centre.
West Brom manager Steve Clarke, a former Chelsea assistant, appeared to have the tactical edge on Chelsea boss Di Matteo, a former West Brom manager.
Despite an early Ryan Bertrand effort cleared off the line by Liam Ridgewell, West Brom had the early ascendancy and it was no surprise to see them go in front.
James Morrison delivered an excellent right-footed cross from the left, David Luiz appeared to switch off briefly and Long met the ball with a downward header that bounced up into the roof of the net.
Chelsea continued to look second best and did not have a shot on target until the 32nd minute, when Sturridge fired straight at Myhill.
Long drilled a diagonal shot wide and had a penalty appeal turned down before Chelsea equalised against the run of play.
Hazard switched the ball for Cesar Azpilicueta on the right and continued his run into the box - arriving at the far post in time to head in the full-back's cross, via a touch off the shoulder of Billy Jones.
Sturridge continued his profligate form early in the second half, as he scooped a left-foot shot at Myhill.
Two minutes later, West Brom were back in front. Some excellent movement saw Long and Odemwingie switch positions, and the Irishman crossed for his colleague who guided a header past Petr Cech from close range.
Di Matteo reacted by introducing Oscar and Mata for Romeu and the underwhelming Fernando Torres.
Immediately Chelsea grew in threat, but with Sturridge now operating as a lone striker they could not convert their chances.
Myhill made one fingertip save from the England forward following Mata's excellent scooped through ball, and another after Mata played Sturridge through one-on-one.
But West Brom kept their shape, and when Sturridge fired yet another chance wide with three minutes to go the game was up - in spite of Cech's late foray into the opposition box.
West Brom go fourth, a point behind Chelsea whose strong start to the season is now a distant memory after a four-game winless streak.
MAN OF THE MATCH
Jonas Olsson: Yet another colossal defensive performance from the Swede, who showed superb positioning and timing in the tackle as West Brom repelled Chelsea's second-half surge.
WEST BROM: Myhill 8, Jones 7, Tamas 7, Olsson 8, Ridgewell 7, Yacob 7, Mulumbu 7, Odemwingie 7, Morrison 7, Gera 7, Long 8. Subs: Dorrans 7, Brunt 7, Rosenberg N/A
CHELSEA: Cech 6, Azpilicueta 7, Cahill 6, Luiz 5, Bertrand 6, Mikel 5, Romeu 5, Sturridge 5, Moses 6, Hazard 6, Torres 5. Subs: Ramires N/A, Mata 8, Oscar 7