Chelsea 1-1 Southampton

Dusan Tadic equalises for Southampton from the spot

• Costa scores his 18th goal of the league season

• Tadic equalises from the spot

• Ivanovic claims for a penalty waved away

• Forster makes several brilliant saves

Chelsea moved six points clear at the top of the Premier League after drawing with Southampton in a superb contest at Stamford Bridge.

Diego Costa gave Chelsea the lead with a header before Dusan Tadic equalised from the spot after Nemanja Matic had fouled forward Sadio Mane.

Southampton keeper Fraser Forster made a series of great saves to deny Oscar and Eden Hazard.

In the closing moments he made a point-blank block from substitute Loic Remy.

Chelsea still have a game in hand on second-placed Manchester City, while Southampton moved into sixth above Tottenham, who later lost 3-0 to Manchester United.

The Blues' remaining major hurdles are Manchester United and Liverpool at home and Arsenal away, but some bookies still have them as 10-1 odds-on favourites for the Premier League, such is the belief that Jose Mourinho will claim his third title in England.

With the League Cup already in the bag, this looks set to be a very successful season for the Portuguese, marred slightly by the blip in midweek when Chelsea were knocked out of the Champions League by Paris St-Germain after drawing at Stamford Bridge on Wednesday.

Mourinho gave 10 of the 11 players that started that match the chance to redeem themselves against the Saints, but the first-half display was poor.

It began well for the home side when the unmarked Costa, who had not scored since January, got on the end of a delightful Ivanovic ball to head in his 18th of the campaign.

However, Southampton were level eight minutes later. Mane, who was a constant menace for centre-backs Gary Cahill and John Terry, found himself sandwiched by Ivanovic and Matic in the penalty area.

Referee Mike Dean awarded a penalty and showed an incensed Matic a yellow card. Tadic was left to despatch the spot-kick.

The Serb was close to adding a second when his angled drive was brilliantly saved by Thibaut Courtois. The Belgian keeper then came to his side's rescue again when his one-handed stop kept out Toby Alderweireld's free-kick.

Chelsea did have a shout for a penalty at 1-1 when Ivanovic's heel appeared to be clipped by Tadic, but the referee waved away the player's appeal.

Mourinho's side needed some inspiration and whatever he said at half-time appeared to do the trick.

The Portuguese brought on Ramires to replace Matic, which gave Chelsea more pace and industry in midfield.

They suddenly looked a different proposition. If only they had not come up against Forster, who was in sparkling form.

The Southampton stopper staked a very strong claim for the England number one jersey with blocks to twice deny Oscar, Eden Hazard and Cesar Azpilicueta, who was agonisingly close to scoring his first league goal for the club.

Sunday's early Premier League contest was a sell-out at Stamford Bridge

The home fans were given some early cheer when Diego Costa headed Chelsea into the lead

Saints were awarded a penalty when Sadio Mane was caught in a Chelsea sandwich and Dusan Tadic converted from the spot

Chelsea improved in the second half but were repeatedly denied by Fraser Forster