Chelsea were thrashed 5-2 by relegation-threatened West Bromwich Albion at Stamford Bridge on Saturday, setting an unfavorable club record.
Christian Pulisic gave Thomas Tuchel's side the lead early on, but Thiago Silva was sent off for two bookable offenses before the 30-minute mark, and the floodgates opened shortly after as Matheus Pereira scored twice just before the break.
Tuchel's first loss since taking over at Chelsea came in humiliating fashion, as Callum Robinson scored a brace and Mbaye Diagne added another in the second half.
The Blues have also set an unwelcome club record for the most goals conceded against a single opponent in a Premier League season, having conceded three goals to the Baggies in a 3-3 draw at The Hawthorns back in September.
Furthermore, the Blues' defense was breached five times at Stamford Bridge for just the second time in the Premier League - nearly ten years since their 5-3 loss to Arsenal in the 2011-12 season - and Tuchel's side had yet to concede a goal at home before Saturday's crushing defeat.
Chelsea stay in the top four of the table after their crushing defeat to Sam Allardyce's side, but West Ham United could leapfrog them if they beat Wolverhampton Wanderers on Monday night.