Guus Hiddink’s unbeaten run came to an end as Chelsea suffered their first defeat in 15 games at Swansea.
Gylfi Sigurdsson’s volley proved the difference between the two sides at the Liberty Stadium to give the Welsh side their maiden victory over the west Londoners.
Chelsea made three changes to the side that crushed Aston Villa last weekend as Asmir Begovic, Oscar and Alexandre came into the starting XI.
Thibaut Courtois and Kenedy dropped to the bench, which was supplemented by youngsters Charlie Colkett, Ola Aina and Kasey Palmer.
Ruben Loftus-Cheek threatened with an early chance but it was Swansea who found the breakthrough midway through the first half in south Wales.
Jefferson Montero caused all sorts of problems down the flank with his cross only half cleared by Matt Miazga and Gylfi Sigurdsson slamming home the loose ball.
Montero was Swansea’s main outlet and gave Cesar Azpilicueta a torrid first 45 minutes as the hosts should probably have led by more than the single goal at the break.
Hiddink showed earlier this season at Southampton that he’s not afraid to hook players at half time and Miazga paid the price for his defensive error by being hauled off.
Kenedy came into the midfield for the second period with John Obi Mikel slotting back into an unrecognisable Blues defence.
Chelsea improved after the break but their 5-0 demolition of the Swans on this ground last season seems years ago now.
The end of term and a fresh approach from incoming manager Antonio Conte can’t come soon enough for the Blues.
Chelsea: Begovic; Azpilicueta, Miazga (Kenedy), Ivanovic, Baba Rahman; Mikel, Fabregas; Pedro, Loftus-Cheek (Falcao), Oscar; Pato (Traore).
Subs (not used): Courtois, Aina, Colkett, Palmer.
