No longer can many ports be considered safe for Andre Villas-Boas in the storm surrounding him. Chelsea had beaten West Bromwich Albion in their previous 15 top-flight meetings and scored more goals against them than any other Premier League side.
But defeat, courtesy of a Gareth McAuley goal eight minutes from time, added further pain to a day that had started going horribly wrong with Arsenal's lunchtime victory at Liverpool. The smoke sensors that did their job amid more high jinks at Chelsea's training ground on Friday are not the only alarms sounding at the club.
There's now clear daylight between the London rivals in the race for the final Champions' League place and neither this result nor the limp performance that brought it about will do anything to reduce the enormous pressure on Villas-Boas.
"It was very poor in all senses of the word," the Portuguese manager said. "It wasn't up to the Chelsea standard. We did extremely badly. West Brom were far superior on the day and full credit to them. They got what they deserved."
Danny Blanchflower was in charge at Stamford Bridge when Albion, by an identical score in March 1979, had last beaten these opponents in the top division. And despite a glaring stoppage-time miss by an otherwise anonymous Frank Lampard, there could be no great argument over the merits of the outcome.
Albion were the better side in the second half, are up four places to ninth and have won three successive Premier League games for the first time since 2002. Roy Hodgson for England, anyone?
As the Albion manager's star rises, the spotlight on a counterpart barely half his age remains intense. The dozens of cameras pointed at the Chelsea dug-out just before kick-off were unlikely to have been for Roberto Di Matteo, warm though the reception was from the stands for the man who led Albion to promotion two years ago.
The Stamford Bridge assistant was quickly reminded that the team he left behind are in good shape as James Morrison's deliberately-sliced 20-yard shot had Petr Cech arching his back to tip over.
Although Marc-Antoine Fortuné snatched at a half-chance that disappeared into the side netting following Gary Cahill's poor attempt at a clearance, Albion were clearly in the mood following their successive four-goal wins over Wolverhampton Wanderers and Sunderland.
They needed to be resolute to keep their goal intact, though, and one headed block by Morrison seemed crucial, with Cahill's free left-foot shot from near the penalty spot apparently on target.
Chelsea edged a first half in which Juan Mata's usually sure touch deserted him as Ben Foster denied him at a tight angle and, either side of the interval, Albion were also reprieved by the wastefulness of Daniel Sturridge. The forward was passed fit despite the toe injury he suffered with England in midweek but he may have wished he had given his native West Midlands a miss after driving wide of a largely unguarded net when picked out by Didier Drogba.
Then, as Steven Reid collapsed in a heap with an ankle problem, Mata curled an inviting pass into his path, only for Sturridge to be outwitted by the out-rushing Foster 30 yards from goal when he was very much first to the ball.
Albion, having threatened just before the break when a shot by the outstanding Youssouf Mulumbu was deflected wide off Cahill, grew in assurance and chances came in abundance. Fortuné smashed straight at Cech following an Ashley Cole error and followed Mulumbu in stretching the keeper from outside the area and Liam Ridgewell skimmed the roof of the net with a header. Keith Andrews was another frequent threat and the substitute Chris Brunt was inches away from marking his return from a two-month foot injury with a goal.
Under pressure from Brunt close in, there was also one brilliant clearance by Cole, who left his side with 10 men when he was helped off in stoppage-time with an ankle problem. But the winner eventually came from an unlikely source.
Andrews helped the ball back in when Brunt's corner was half-cleared by Cech and although Ridgewell's shot was going wide, McAuley stretched to turn it home left-footed from four yards. At the end, Lampard side-footed Cole's pull-back wide from six yards and that was that. AVB KO'd by WBA.
"Of course I sympathise and empathise with him," said Hodgson, some 14 months on from finding himself under similar criticism at Liverpool. "Football isn't about unmitigated success. There are moments of failure in your career as well.
"Andre has been very successful and has come here with high expectations. It hasn't gone as well as he would have liked but it is early days. We played well. It was a good performance from start to finish."
West Bromwich (4-3-3): Foster; Reid (Tamas 57), McAuley, Olsson, Ridgewell; Andrews, Mulumbu, Morrison; Odemwingie, Fortune (Long 84), Thomas (Brunt 63).
Chelsea (4-3-3): Cech; Ivanovic (Meireles 84), Cahill, Luiz, Cole; Ramires, Essien (Torres 76), Lampard; Sturridge (Malouda 63), Drogba, Mata.
Referee Phil Dowd.
Man of the match Mulumbu (West Bromwich).
Match rating 7/10.
Brits in Europe
Arsenal (0) v Milan (4) (7.45pm, Sky Sports 2)
It was eight years ago that Milan lost a 4-1 first-leg lead to Deportivo la Coruna, who overran them 4-0 to go through. Arsenal, unfortunately, do not have even the one away goal and cannot be relied on for a clean sheet. But manager Arsène Wenger believes: "You can realise the impossible when you don't know it is impossible. Let's ignore the statistics and just go for it."
Sporting Lisbon v Manchester City (6pm, ITV4)
After seeing off the Portuguese league leaders Porto comfortably enough, City take on Sporting, who trail them by more than 10 points. But the Lisbon side do have a good home record in Europe stretching to nine games unbeaten, including the 1-0 defeat of Legia Warsaw in the last round. They are likely to field former Liverpool defender Emiliano Insua.
Manchester United v Athletic Bilbao (8.05pm, Five)
United have lost more games than they have won against Spanish opposition, although usually against the big two rather than the Basque club with the English name, who were founded in the 1890s by British shipyard workers. They sit in the top six in La Liga and qualified narrowly thanks to an away goal on Lokomotiv Moscow's artificial pitch by Iker Muniain. United will want a cushion for the second leg.
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