James McClean halted Chelsea’s rise up the Premier League table as West Brom came from behind twice to secure a 2-2 draw at Stamford Bridge.
West Brom created a handful of early chances but the hosts took the lead through an unlikely source in Azpilicueta, who found the back of the net after bombing forward to meet a cross at the far post.
The Baggies responded well to the early setback and hauled themselves level when Craig Gardner’s driven shot from the edge of the area nestled into the bottom corner.
Guus Hiddink’s side took the lead once again in the 73rd minute after Gareth McAuley turned the ball into the his own net when trying to prevent Kenedy from connecting with Willian’s low cross.
The Baggies came from behind for a second time when McClean struck four minutes from time as the visitors earned a deserved point.
Chelsea felt aggrieved and Diego Costa made his frustrations known at the final whistle by arguing with Baggies players.
Costa felt Claudio Yacob, already booked for a first-half foul, should have received a second yellow card for an off-the-ball trip on him early in the second half.
The midfielder was promptly substituted and referee Anthony Taylor was barracked by Chelsea players and supporters thereafter.
The Blues are unbeaten in six games since the departure of Jose Mourinho, but Guus Hiddink’s hopes of a top-four finish receded further in front of owner Roman Abramovich and ahead of Saturday’s clash with Everton.
Chelsea began well. Costa glided by Jonny Evans but shot wide and Willian fired off target either side of McClean heading off target from Darren Fletcher’s cross.
James Morrison departed with an apparent hamstring problem before Azpilicueta blocked a Fletcher effort and then scored at the other end.
Azpilicueta is less than prolific, but likes scoring against West Brom.
The full-back, who netted at The Hawthorns in August, claimed his first goal at Stamford Bridge when he prodded in Branislav Ivanovic’s cross at the back post.
There were holes aplenty in the visiting defence, but Chelsea’s rearguard was porous too.
The Baggies breached and exposed when Pedro gave the ball away to Fletcher, who was influential for the visitors.
Fletcher prodded it to Gardner, who did the rest, shooting into the bottom corner from 25 yards.
Costa ballooned an effort over and Salomon Rondon shot just wide as both sides had chances to take an interval lead.
Pedro made his debut at The Hawthorns and inspired Chelsea to a first win of the season, but his star has faded since.
The subdued Spain winger was withdrawn for Kenedy at half-time and the Brazilian gave Chelsea much-needed pace and penetration in an increasingly disjointed contest.
Costa had no complaints when he was booked for a poor lunge on Gardner after losing control of the ball.
Kenedy next powered down the left and Costa looked to join the attack, only to tumble in front of Yacob.
The Baggies midfielder avoided punishment, prompting Chelsea complaints led by captain John Terry. Yacob did go off, substituted for Saido Berahino.
Chelsea continued to press, with a deflected Costa effort going into the side-netting.
McClean was then booked for squaring up to Thibaut Courtois as the contest became more niggly still.
Chelsea took the lead for a second time when Willian’s cross deflected in off McAuley, who was under pressure from Kenedy.
Costa was denied and Kenedy shot wide before McClean equalised from the edge of the area after Chelsea twice failed to clear.