Southampton deepened the gloom at Chelsea with a fully deserved 3-1 victory over the Premier League champions at Stamford Bridge.
The Saints had to come from behind in west London after Willian’s early free kick put the Blues ahead, but Steve Davis expertly equalised before half time.
Sadio Mane edged the visitors in front after poor defending from John Terry before Graziano Pelle completed the scoring after a fine breakaway move.
The defeat leaves Jose Mourinho’s side languishing in the doldrums of the Premier League table after a fourth defeat in seven games.
Mourinho restored captain Terry to the starting XI in an attempt to shore up the home defence, and Willian’s brilliant free kick appeared to give them the perfect platform for a second consecutive home league success.
The Brazilian is making a name for himself from dead ball situations, and his perfectly-executed effort after just nine minutes was his fourth goal from a free kick in as many games.
Southampton then started to grow into the game and Mane, who terrorised Terry and Gary Cahill throughout, will feel aggrieved that he wasn’t awarded a penalty after going down following contact from Ramires.
But the Saints did equalise just before the break, Davis powering home a sublime volley after Pelle had shrugged off the attentions of Cahill.
Soon after half time, Begovic was quick off his line to make a smart stop from Mane, but the Senegalese wasn’t to be denied for too long.
After Radamel Falcao was dubiously booked for simulation by referee Robert Madley, Mane rolled a naïve lunge from Terry before squeezing his shot under Begovic on the hour mark.
Mourinho introduced Pedro for goalscorer Willian and was greeted by a chorus of boos and, to make matters worse, Southampton extended their lead with just under 20 minutes remaining.
After the abject Eden Hazard squandered possession on halfway, the Saints broke quickly and Pelle capped a fine counter with a clinical finish across the despairing Begovic.
Falcao had a late free kick deflected just over Martin Stekelenburg’s crossbar but, in truth, the Blues never looked like mounting a fightback as their dire start to the season continued.
