Chelsea are 110 years old: and they look every day of it, battling towards a third Premier League title under Jose Mourinho. Six points clear with a game in hand hardly constitutes a crisis. Mourinho would certainly have bought that at the start of the season, any manager would. Yet it is hard, hard going, for a team that once seemed so assured. Southampton had the better of the first-half here, and all Chelsea’s pressure could not conjure a winner after half-time. Click here to read Martin Samuel's full match report . Host commentator . Chelsea miss the chance to go eight points clear at the top of the Barclays Premier League table as Southampton claim a point at Stamford Bridge. And Koeman's side were worthy of the point as they impressed throughout the 90 minutes. Costa put his side in the lead, however his effort was cancelled out when the Saints were awarded a first-half penalty which Tadic converted. Azpilicueta came close to scoring a late winner however Forster was able to beat the ball away for a corner. Terry then almost gets on the scoresheet with a driven effort at goal, however he is unable to find a way past Forster. Pelle has just played a delightful lobbed pass to Mane but the Senegal international is unable to get the ball under control when going through on goal. Remains 1-1 at Stamford Bridge. Chelsea have just five more minutes to open up an eight-point lead over Manchester City. The Blues still have another game in hand over the Premier League champions so it's not all doom and gloom for Mourinho's men. Pelle has eight minutes to try to score a winner for his side. Meanwhile Willian is replaced by Cuadrado after hobbling off injured. With both sides having terrific records when it comes to keeping out the opposition I think the next goal will win this game. Chelsea look more likely to grab a winner as Southampton have been pushed back during the second half. There's just under 12 minutes left at Stamford Bridge. Hazard calls Forster into action with a quick fire shot. However the England stopper stands tall to deny the Belgium international. Tadic and Davis off, Djuricic and Ward-Prowse on . Cahill has been cautioned for yet another foul on Mane. The Senegal international has been in impressive this afternoon. Koeman will be thinking his side may be able to nick all three points. Pelle is warming up on the Stamford Bridge touchline. Long has led the line well but Koeman may look to freshen things up. Mane continues to cause problems with his blistering pace. This time it was Ivanovic who hacked Mane down as he was running through on goal. Wanyama also goes into Dean's book for a late foul. Mourinho brought in Cuadrado during the January transfer window to improve his wide options but the Colombia international hasn't really been handed the opportunities to impress. Today may just be the day for Cuadrado to prove his worth. Costa came close to grabbing his second goal of the match. The Spain international, who was involved in a tussle with Fonte, tried to poke home a cross by Willian but his effort hit the woodwork. Mourinho has decided not to risk the chance of Matic seeing red as he has replaced him with Ramires. Chelsea have started the second half in lively fashion. Their flair players are linking up much better than they were during the latter stages of the first. Sportsmail's Graham Poll believes Matic should have been sent off the foul on Mane. Matic was lucky not have been given a yellow card for a clumsy challenge on Mane. Dean appeared to reach into pocket before changing his mind. Chelsea played some nice football in the early stages of today's match. Costa's goal came after an intricate move which led to Ivanovic crossing into the box. Chelsea have looked extremely lacklustre since conceding. Matic deserved to be penalised for his foul on Mane despite Chelsea's protests. The home side could have also been awarded a penalty during the first half when Ivanovic was fouled inside the area. Mourinho will be weighing up his options ahead of the interval. Both Fabregas and Oscar have failed to make any real impact on today's game so far. Ramires, who failed to impress in midweek, and Cuadrado are both viable options from the bench. Koeman appears to have made the right decision in picking Long over Pelle. Long's pace is causing Terry and Cahill problems and his link up play with Mane has been exceptional thus far. The Saints look the more likely side to score the next goal. After a tricky first five minutes when it looked like Willian was going to run riot, Koeman's side have settled down and look a real threat on the counter attack. Mane has been cautioned for a late foul on Ivanovic. Chelsea could have received a penalty of their own. Ivanovic appeared to be clipped by Tadic while the right back was making his way into the penalty box. Mourinho will not be happy with Dean's decision. Tadic slots home via the foot of Courtois to level the scoreline at Stamford Bridge. Matic, who received a yellow card after being penalised by Mike Dean, appeared to win the ball but went through the back of Mane. Southampton have been awarded a penalty. Matic made a lunging challenge on Mane. Costa came into today's game level with Manchester City's Sergio Aguero as the joint highest goalscorer with 17 goals. However the Spain international's goal puts him in the lead. Southampton go up the other end in hope of getting back on to level terms. Mane shoots at goal but Courtois manages to get down to palm away his effort. And there you have it. Ivanovic crosses the ball into the box from the right and Costa has the easy task of nodding into the net. Koeman will be wondering why he was allowed to rise above his side's defence without being challenged. The Premier League's meanest defence will have to find a way of keeping Diego Costa quiet. Costa has had a remarkable first season in England - with the former Atletico Madrid man scoring 17 league goals. Brazilian playmaker Willian has looked extremely lively during the early exchanges. He has popped up on the right and through the middles to cause Southampton's defence problems. The likes of Willian, Oscar and Hazard have shown some neat early touches. Willian just ran through the middle before laying the ball onto Azpilicueta however his shot went over the bar. Chelsea and Southampton have excellent records when it comes to keeping out the opposition. Koeman's side have conceded just 20 Premier League goals while the Blues have let in just two more than their opponents. Ronald Koeman: 'It is always a bad time to face Chelsea because they are the strongest in the Premier League. 'It is a great opportunity for Chelsea after Man City's loss against Burnley and we have to stop them. We have to be patient and good defending will be important for today.' Chelsea seem to enjoy playing in front of their own fans. They have not lost a home match in the Premier League this season - with their only defeat at Stamford Bridge coming against Bradford in the fourth round of the FA Cup. Jose Mourinho: 'I'm not like the wind. I have stability in my relationship with the players. I trust my team. This is why I have gone with 10 of the 11 players which started against PSG.' Cesc Fabregas came in for criticism after Chelsea's defeat by PSG and he has a history of petering out in the second half of the season. Read the evidence here: http://www.dailymail.co.uk/sport/football/article-2991402/Cesc-Fabregas-history-fading-second-half-season-Chelsea-seen-slump-coming.html . John Terry: 'We came in for a lot of criticism after the PSG game and rightly so. 'If someone would have said at the start of the season that we would have won the Capital One Cup and where we are in the league then we would have bitten your hand off.' Chelsea fans turned up in their droves early on to get a glimpse of the players as they left the team coach. Let's see if the likes of John Terry, Eden Hazard and Co will be able to get out of first gear after stalling against PSG. If you are thinking about making a late trip up to Stamford Bridge without a matchday ticket then you best turn back as today's match is a sell out. However, have no fear as I will be providing live updates on today's early kick-off. Ramires is replaced by fellow countryman Willian in Chelsea's starting line-up after starting against PSG. Chelsea subs: Cech, Filipe Luis, Zouma, Ramires, Cuadrado, Remy, Drogba . Graziano Pelle also drops down to the bench for the Saints as Shane Long is given the nod to lead the line at Stamford Bridge. Southampton subs: K. Davis, Yoshida, Gardos, Djuricic, Ward-Prowse, Pelle, Targett . Chelsea XI: Courtois; Ivanovic, Cahill, Terry, Azpilicueta; Matic, Fabregas; Willian, Oscar, Hazard; Costa . Southampton XI: Forster; Clyne, Fonte, Alderweireld, Bertrand; Wanyama, Schneiderlin; S. Davis, Tadic, Mane; Long . Chelsea's attention switches back to the Barclays Premier League following their disappointing exit from the Champions League on Wednesday. Jose Mourinho's side have the opportunity of extending their lead over Manchester City after Manuel Pellegrini's side slipped up against Burnley. Follow all the action here as Sportsmail provides live commentary of today's match at Stamford Bridge. Chelsea will be hoping to get back to winning ways during Sunday's match against Southampton after crashing out of the Champions League  in midweek. The Blues can open up an eight-point lead over current Barclays Premier League champions Manchester City with a victory against Southampton. However Ronald Koeman's side will be no easy ride as they have shown they are capable of mixing it up with the big boys. In fact, they claimed a point against Chelsea on December 28 when the two sides drew 1-1 at St Mary's.
Diego Costa scored his 18th Premier League goal of the season . Dusan Tadic levelled the scoreline in the 19th minute from penalty spot . Nemanja Matic was penalised for foul on Southampton's Sadio Mane . Chelsea XI: Courtois; Ivanovic, Cahill, Terry, Azpilicueta; Matic, Fabregas; Willian, Oscar, Hazard; Costa . Southampton XI: Forster; Clyne, Fonte, Alderweireld, Bertrand; Wanyama, Schneiderlin; S. Davis, Tadic, Mane; Long . Southampton claimed a point against Chelsea at St Mary's in December .