SOUTHAMPTON 1 (Sadio Mane 17)
CHELSEA 1 (Eden Hazard 45+1)
Just two days earlier, Chelsea had looked invincible. At Southampton last night, they seemed invisible.
The Blues battered West Ham on Boxing Day. At St Mary's, they pulled a late Christmas cracker with a bad joke.
Apart from Eden Hazard, the magicians left their wands under the Christmas trees back in London.
They were present in body, but the magic was missing.
Andre Schuerrle was so anonymous he was withdrawn at half-time to spare further embarrassment.
Cesc Fabregas and Nemanja Matic were effectively straitjacketed and Diego Costa struggled to keep his feet (quite literally on a couple of occasions).
Southampton's last-ditch defending was superb, but Jose Mourinho may wonder where his side's characteristic fortitude went.
They will still end the year in first place. But they faltered. The mask slipped a little. Their typical fightback deserted them. They looked human. That will infuriate Mourinho.
In fact, his favoured Superman left his cape behind. At St Mary's, Chelsea's captain appeared vulnerable.
In a week when his manager has been championing his refusal to grow old disgracefully, John Terry found himself caught short.
As Dusan Tadic prepared to a dink the kind of perfect chip usually associated with sand wedges, Terry stepped forward and called for offside.
In that moment, he was lost.
He was out of sync with the offside line and out of time to catch the galloping Sadio Mane.
The Saints forward left Terry for dead, racing clear before chipping the ball past Thibaut Courtois in the 17th minute.
All season long, Chelsea's back four have defined organisation, but they scattered like bowling pins in a single Southampton strike.
The Saints hounded them.
Much has been made of Ronald Koeman's emphasis on eye-catching play, but his Saints march with real men of muscle.
Mane was a monstrous presence, second only to Victor Wanyama in his ability to terrorise. Mane made a mess of the fullbacks. Wanyama made Nemanja Matic look mortal.