Chelsea extended their lead to six points over Manchester City at the top of the Premier League but were held to a 1-1 draw by Southampton at Stamford Bridge.
The home side struggled to find their feet in the opening stages of the game, although, with just 11 minutes on the clock, they managed to edge ahead 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 Serb latched onto Sadio Mane's flick to curl an effort wide of goal with his follow-up attempt.
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 penalty spot, straight down the middle, after Nemanja Matic was adjudged to have felled Mane inside the box.
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.
In the second half, Chelsea were inches away from retaking the lead when Wilian blasted a shot, which Costa managed to divert towards goal with his right foot, but the ball cannoned off the post following a further deflection.
Tadic almost carved out a moment of magic for the Saints when he used good skill to beat two defenders in the box before teeing up Long, but his strike was well blocked by Gary Cahill.
The Blues spurned the chance to pull ahead as Willian lifted a pinpoint cross onto the head of Oscar, but the midfielder could only head straight at Forster, while Eden Hazard failed to turn the rebound home from a tight angle.
Oscar was presented with another opportunity minutes later when he drove forward down the left and blasted a strike towards goal, which forced Forster into another fine stop.
As Jose Mourinho's men pushed forward for a winner they left gaps open at the back for Mane to exploit, but he blazed his first attempt over the bar, while, on a second break, the forward lost control of the ball at the vital moment.
Chelsea made one last surge forward, but were denied a late winner as Forster made a good reaction save to deny Loic Remy, and, from the rebound, John Terry's first strike hit Cahill on the line and his second went wide of the post.
The Saints held out for the draw, leaving Mourinho's men to rue their missed chances as they failed to take full advantage of Manchester City's defeat to Burnley, adding just a point to their lead at the top of the Premier League.
