Chelsea appear to be suffering from a Champions League hangover having produced an underwhelming performance to go into half time level at 1-1 against Southampton.

The home side struggled to find their feet in the opening stages of the game, although they managed to edge ahead with just 11 minutes on the clock courtesy of Diego Costa's first goal in seven outings.

Branislav Ivanovic created the opening for his teammate, swinging a cross into the middle which the unmarked Spaniard headed beyond a rather helpless Fraser Forster.

Despite the early setback, Southampton soon grew into the game themselves, coming close to levelling things up almost instantly when Dusan Tadic forced Thibaut Courtois into making a solid stop down low. The danger did not end there for Chelsea, though, as the Serbian latched onto Sadio Mane's flick to curl a follow-up attempt wide.

The Saints, who have won just one of their last 11 meetings against the current league leaders, did manage to bring the score level on 19 minutes when Tadic just about converted from the spot, straight down the middle, after Nemanja Matic was adjudged to have felled Mane inside the box.

Ivanovic saw a penalty appeal of his own turned down when he was caught by countryman Tadic, while the lively Southampton man was involved again soon after up the other end when he forced Courtois into making another save.

Costa headed the Blues' best chance to retake a first-half lead wide, but the better openings fell the way of the visitors, who ended the opening 45 minutes on top.

Courtois had to be alert to hack the ball clear at his front post following a scare at the back, before Mane got the ball stuck under his feet when played into a good position by Shane Long.