Brentford substitute Fabio Carvalho tapped in an 93th-minute equaliser to deny Chelsea victory in a dramatic London derby.
Carvalho, 23, had been on the pitch for less than four minutes before turning in from a long Kevin Schade throw-in.
It had looked as if Chelsea substitutes Cole Palmer and Alejandro Garnacho would steal the headlines.
With the visitors a goal down, Palmer swept in a first-time volley to equalise just after the hour mark, having only been on for five minutes.
Then Garnacho, recently signed from Manchester United, helped set up midfielder Moises Caicedo to power in a shot past Brentford goalkeeper Caoimhin Kelleher in the 85th minute.
Brentford had deserved their half-time lead – forward Schade struck in the 35th minute shot after Jordan Henderson’s long ball had sparked a counter-attack.
Chelsea head coach Enzo Maresca dipped into his vast playing resources by making three half-time changes in response.
Reece James, Marc Cucurella and Tyrique George came on for debutant Facundo Buonanotte, a deadline-day loan signing from Brighton, Jorrel Hato, another new arrival, and Wesley Fofana, making his first start since recovering from a major hamstring injury.
Maresca had picked a starting line-up with the aim of resting key players for their return to the Champions League after a two-year absence this week. But it didn’t work, and he had to call on them – with Palmer also coming on early in the second half to replace winger Jamie Gittens.
Chelsea remain fifth after four Premier League matches – and now turn their attentions to Bayern Munich in the Champions League, before returning to domestic action against Manchester United. Brentford, meanwhile, sit 12th.
