Substitute Danny Welbeck scored a dramatic stoppage-time equaliser for Brighton to deny Chelsea victory and deal a blow to their hopes of keeping pace with Manchester City at the top of the Premier League.
Chelsea looked set to move three points clear of fellow title contenders Liverpool when Romelu Lukaku marked his first top-flight start for two months by giving his side a lead, which they held until the 91st minute.
Brighton carved out 18 chances in total at Stamford Bridge but looked set for disappointment before Welbeck met Marc Cucurella’s chipped cross.
On a bad night for Chelsea, they also lost defenders Reece James and Andreas Christensen to injury.
They head into 2022 second in the table – one point above third-placed Liverpool, who they face on Sunday at Stamford Bridge (16:30 GMT).
But they trail Manchester City by eight points after Pep Guardiola’s side won 1-0 at Brentford.