Thomas Tuchel's start to life as Chelsea manager could not have gone much better. After 14 matches the German was unbeaten, had revived the club's Premier League top four ambitions, guided a march into the FA Cup semi-finals, and safely secured passage to the Champions League quarter-finals. So when a struggling West Bromwich Albion side, fast running out of time to preserve their top flight status, paid a visit to Stamford Bridge on Saturday afternoon, it was all set up to be another routine win for Tuchel. After 27 minutes, when American winger Christian Pulisic pounced on a fingertip save by West Brom goalkeeper Sam Johnstone to give Chelsea the lead, there was little to suggest any other outcome than an 11th win in all competitions for Tuchel and, most likely, a clean sheet to boot. After all, Chelsea had conceded just twice since the German replaced Frank Lampard, while West Brom had scored just once in their past five outings. Instead, what transpired over the subsequent 63-plus minutes would throw all form, and logic, right out the window. For Chelsea, it started to unravel less than 150 seconds after Pulisic's opener when Thiago Silva, the typically classy and composed Brazilian defender, was given his marching orders for a second yellow card offence. Silva has been exceptional for Chelsea since his arrival last summer but the former Paris Saint-Germain captain has endured two nightmare moments. The first came on debut when a loose pass led directly to a goal, the second was this reckless red card. Both came against West Brom. Dealing with a numerical disadvantage, Chelsea held firm and attempted to hit West Brom on the break as the visitors pressed forward. But as the game opened up, two minutes of mayhem in first half stoppage time would set the scene for the rest of the match. Matheus Pereira levelled for West Brom when he latched on to a long range Johnstone pass and lobbed Chelsea keeper Edouard Mendy, before the Brazilian midfielder struck again two minutes later to give the Baggies the lead. "We were unable to cope with the red card. I don't know why. We gave away two very easy goals," Tuchel said. Even so, Chelsea would have been confident of getting something out of the match when the teams emerged for the second half. But West Brom refused to sit on their lead and struck twice on the counter-attack five minutes apart, with Callum Robinson volleying home a Darnell Furlong cross before Pereira turned provider for Mbaye Diagne. Chelsea pulled one back to make it 4-2 when Timo Werner set up Mason Mount for a simple tap-in but West Brom scored their fifth in stoppage time when Robinson chipped onrushing Mendy. If Silva has cause to despise facing West Brom, conversely Robinson must wish he could play the Blues every week. The English forward has scored four Premier League goals this season, all against Chelsea. It was the worst possible preparation for Chelsea's Champions League quarter-final first leg against Porto on Wednesday, while fifth-placed West Ham can move one point ahead and Tottenham, in sixth, can move level with Chelsea if they both win this weekend. "It's important we digest it. I did not see it coming, now we have to take our responsibilities – me included – and shake it off," Tuchel said. "It's a wake-up call. We will get the right response." For West Brom, the result will undoubtedly be an enormous morale booster but there is still plenty of work to be done to avoid relegation. Sam Allardyce's team stay second bottom and are seven points adrift of 17th-placed Newcastle. "People will always look to the fact they went down to 10 men but I thought we started the game brightly and created chances. I thought Thiago Silva was lucky to stay on after the first foul," Allardyce said. "Our goals were all quality goals, not just the finishing but the build-ups. It's just a bit of a shame we didn't show that quality in some others games but this still gives us a bit of hope."