Frank Lampard gave Thiago Silva a Premier League debut and the captain’s armband, while Willy Caballero was given the nod to start ahead of Kepa Arrizabalaga in goal, with new signing Edouard Mendy not yet ready to be involved.
It took just four minutes for the Argentine to be picking the ball out of his own net after Marcos Alonso’s poor header gifted West Brom possession and Robinson profited from some passive defending by Reece James to swivel and fire home.
Abraham’s excellent performance in the Carabao Cup thrashing of Barnsley had earned him a start, but he wasted a glorious chance to hit straight back, guiding over from James’ terrific early cross, before Timo Werner cushioned a volley against the bar.
Just as an equaliser was looking inevitable, however, Chelsea hit the self-destruct button, conceding twice in three minutes to leave themselves a mountain to climb.
First, Silva miscontrolled, letting the ball roll under his foot to allow Robinson – whose only Premier League goal last season had come against Chelsea – to race away and beat Caballero again.
Then, the Blues’ set-piece vulnerability surfaced once more, as Darnell Furlong headed a corner on to the back post where Alonso had left Bartley completely unmarked to tuck away a third, with James also guilty of ball-watching.
Lampard reacted by hauling off the woeful Alonso and Mateo Kovacic, who had been sloppy in possession, and sending on Cesar Azpilicueta and Hudson-Odoi at the break.
Mount gave Chelsea hope ten minutes after the restart with a sweet strike that left Sam Johnstone rooted to the spot as it whistled in at the near post, though the ‘keeper did well to palm away Kai Havertz’s deflected shot moments later.
The German played a key part in the terrific goal that made it 3-2, laying a delightful return pass into the path of Hudson-Odoi, who slotted into the far corner to set up a tense final 20 minutes.
Slaven Bilic’s men were on the verge of holding out to pick up their first win since returning to the top-flight when Johnstone parried Mount’s low shot and Abraham reacted to tap into an empty net.