Chelsea moved six points clear at the top of the Premier League after drawing with Southampton in what was a superb contest at Stamford Bridge.
Diego Costa gave Chelsea the lead with a header before Dusan Tasic 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 above Tottenham into sixth, ahead of the Londoners’ later game against Manchester United.
The Blues remain the likely league champions, but they cannot afford too many repeats of what was a very poor first-half display on Sunday.
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.
Jose 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.
Taking the second-half chances into account, Mourinho will rue his side failing to grab all three points, but on reflection a point each was probably a fair result.