Callum Robinson scored a brace as Chelsea come from a three goals down at half-time to draw 3-3 at Hawthrons.
Robinson gave West Bromwich Albion the lead, four minute into the first-half, when a poor header for Marcos Alonoso allowed Matheus Pereira to pick out Callum Robinson to provide a fine finish across Willy Caballero.
Robinson completed his brace in the 25th minute and three minute later Kyle Bartley makes it 3-0 for the Baggies.
Frank Lampard make two quick substitutions at the beginning of the second half, bringing in Cesar Azpilicueta and Hudson-Odoi for Marcos Alnoso and Mateo Kovacic.
Mason Mount scored in the 55th minute to gave the Blues a bit of hope, substitute Hudson-Odoi added another goal in the 70th minutes and Tammy Abraham completed the come back for Chelsea when he scored in the 90th minutes.
Chelsea becomes the first Premier League team since West Ham on February 2011 to avoid defeat after trailing by 3+ at half-time, a game which was also 3-3 against West Brom at Hawthrons.
West Brom are the first top-flight side to concede 11 goals in their opening three league games since Arsenal in 1963-64 (12)
Chelsea will now turn their attention to Tuesday’s EFL Cup fourth-round game against Tottenham, while West Brom will face Southampton in the Premier League on Sunday October 4.