Matheus Pereira and Callum Robinson scored twice as struggling West Brom overwhelmed 10-man Chelsea and emphatically ended the 14-match unbeaten start to Thomas Tuchel's tenure at Stamford Bridge. The Baggies were as brilliant as the Blues, who had Thiago Silva sent off in the 29th minute, were abject. The result moves the 19th-placed side to within seven points of 17th-placed Newcastle, and even if they do not manage the improbable and escape relegation, they will look back on this day with great pride. Sam Allardyce's men were outstanding on the counter-attack and each of their goals was of high quality. Chelsea took an undeserved lead in the 27th minute when Christian Pulisic followed up after Marcos Alonso's free-kick came off the post. However, two minutes later their day started to take a turn for the worse when Thiago was shown a second yellow for a rash challenge on Okay Yokuslu. That was followed by a horror show in first-half stoppage time as Pereira took centre stage. The Brazilian's first effort was a cute finish over Edouard Mendy before he finished off a gorgeous move with a low strike between three defenders. In between those goals, Matt Phillips produced a strike that came off the woodwork. West Brom then went for the jugular after the break as substitute Robinson made it 3-1 with a sensational side-foot volley before Mbaye Diagne finished off a sweet move with an even sweeter strike. England midfielder Mason Mount, brought on at half-time, tapped in to reduce the deficit but the Baggies resisted other Chelsea threats before Robinson capped off a great day for the visitors with a clipped finish. Sluggish Chelsea pay the price Was this Thomas Tuchel's first major tactical misjudgement? His reasons for leaving some first-team regulars from the first XI, including Mount and Kai Havertz, was because he wanted the freshest legs on the pitch because of the extra exertions of his benched players during the international break. Those who started might have been sharper physically, but they were mentally sluggish at times with Thiago paying the biggest price. It was a risk to start the 36-year-old Brazilian, who had just returned from two months out with an injury. He took 'one for the team' when he pulled back Pereira on the edge of the area, but his second booking was inexcusable for a player of his stature. Dane Andreas Christensen, who had deputised for Thiago, came on as midfielder Hakim Ziyech made way. Striker Timo Werner came into the match short of confidence and having missed a 'sitter' for Germany against North Macedonia. He probably wished he reacted as quickly as Pulisic did for the Blues goal, although he did set up Mount's goal. By that stage, both he and his team-mates were probably wishing they were still on international duty. A side who had conceded only two goals in Tuchel's previous 14 games were outwitted and embarrassed by one who had struggled to score this season. Chelsea have four days to recover before they face Porto in the Champions League quarter-finals. West Brom attack dazzle at Stamford Bridge This was the perfect storm for West Brom - a day when their players were on song in contrast to their counterparts. Pereira has been one of the shining lights for the Baggies during this difficult season, and even though he only signed a permanent deal last summer it might prove difficult to hang on to him if they go down. The timing of his run for the first goal from goalkeeper Sam Johnstone's punt downfield was perfection, as was his clinical finish for the second. Robinson, who only came on in the 37th minute for the injured Branislav Ivanovic, immediately adapted to the momentum of his team. His finish for West Brom's third was the pick of the bunch. Allardyce has never experienced relegation from the Premier League during his long managerial career - if he maintains that record this season then it will arguably be his greatest feat.