Chelsea 1-1 Southampton: Dusan Tadic's penalty cancels out Diego Costa's opening goal

• Chelsea 1-1 Southampton - in pictures >>

For the second time this season, nothing could separate the teams after a breathless encounter, in which Ronald Koeman’s men came from behind to earn what could be a crucial point.

Diego Costa had headed the Blues in front after 11 minutes, only for Dusan Tadic to level from the penalty spot shortly afterwards, after Sadio Mane was fouled by Nemanja Matic.

The game was end-to-end from thereon in, with Saints holding firm to move up to sixth in the table, at least for a few hours.

Koeman made a big call before kick-off, dropping Graziano Pelle, who hadn’t scored in the league since before Christmas, and replacing him with Shane Long.

Toby Alderweireld also returned to the line-up for the first time since suffering a hamstring injury in the 1-0 win at Manchester United in early January.

Elsewhere, Tadic and Steven Davis came back in, with Eljero Elia, who suffered an ankle injury in training, and Filip Djuricic dropping out.

Despite the return of Alderweireld, Saints conceded one of the softest goals they have done all season, after 11 minutes.

Branislav Ivanovic sent in a lofted cross from the right that should really have offered little danger, but Fraser Forster stayed put and Costa drifted in between Nathaniel Clyne and Toby Alderweireld to head back across goal from six yards.

Saints almost equalised immediately, as Ryan Bertrand, who was applauded by the home fans before kick-off on the return to his old club, sent an angled pass to the byline for Tadic, who cut it back into the path of Mane, but Thibaut Courtois made a superb save from his low, left-foot shot.

Koeman’s men didn’t have to wait long, however, as they levelled the match from the penalty spot in the 19th minute.

Mane played a one-two with Victor Wanyama and, as he drove into the box, he was judged by referee Mike Dean to have been brought down by a sliding Matic, who was booked for the offence.

Tadic, who missed a penalty earlier in the season at Burnley, might have had his heart in his mouth as Courtois’ trailing leg made contact with his effort down the middle, but it wasn’t enough to keep it out.

Chelsea then wanted a penalty for Tadic standing on Ivanovic’s ankle in the area, but nothing was given, despite his fellow Serbian’s dramatic tumble.

After Mane was then booked for a foul on Ivanovic, Tadic nearly scored a second, receiving a pass down the inside-left from the Senegal international and sending in a driven effort, only for a diving Courtois to save.

Saints really were swarming all over Chelsea at this point, and Bertrand caused havoc in their area when he got to the byline and sent a low ball in.

Shane Long nearly got on the end of it, but a combination of Courtois, Gary Cahill and John Terry unconvincingly scrambled it away after a few failed attempts.

Morgan Schneiderlin, immense in midfield in the first half, then had an opportunity from a well-worked corner, but his right-footed effort from Steven Davis’ driven delivery flew wide of the near post.

The Chelsea fans were becoming extremely agitated and, as the half-time whistle, it was some compliment to the performance of Koeman’s men that they were perhaps the most disappointed with the scoreline.

Despite the chance for Jose Mourinho to sort things out at the interval, the second half began much in the way as the first ended.

Matic was so fortunate to avoid a second yellow for bringing down Mane 25 yards out, while Saints almost scored from the resulting free-kick.

Davis shifted the ball to Alderweireld, who unleashed a stunning right-footed effort that arrowed towards the top corner, only for Courtois to make a superb stop.

From the rebound, Mane attempted a spectacular bicycle kick, but that was brilliantly blocked by Cahill.

Mourinho made his first change, unsurprisingly taking off Matic, who was surely out of lives, and replacing him with Ramires in the 54th minute.

Immediately, Chelsea took control and put Saints under enormous pressure.

Jose Fonte had to make a brilliant last-ditch tackle to keep out Costa, before the striker then diverted Willian’s mis-hit shot onto the post from close range.

Wanyama and Ivanovic both went into Dean’s book within seconds of each other, for separate tackles, as the frantic pace continued.

Cahill was cautioned too, in the 68th minute, as the irrepressible Mane breezed past him down the left and was bundled over just outside the area. The resulting free-kick, unfortunately, came to nothing.

With just under 20 minutes remaining, Koeman made his first changes, bringing off Davis and Tadic, and putting on James Ward-Prowse and Djuricic.

Forster had to make a brilliant double save, keeping out Oscar’s header from Willian’s cross, before turning away Hazard’s rebound from a tight angle.

He was called into action again with 15 minutes left, saving one-on-one from Oscar, after Hazard had slipped him in.

Fonte then made a superb diving block to deflect a Costa shot over the bar, before Mourinho replaced Oscar with Loic Remy.

Djuricic was booked for a foul on Willian, before Koeman sent on Pelle for Long and Mourinho replaced Willian with Juan Cuadrado.

Mane nearly got in with three minutes left, but couldn’t control Pelle’s lofted ball over the top, as the chance disappeared.

As the clocked ticked past 90 minutes, Chelsea went so close to breaking the deadlock.

After Forster turned a Cesar Azpilicueta shot round the near post, the resulting corner fell to Juan Cuadrado in space.

His low shot was beaten away by Forster, only for the rebound too fall to Terry. His goalbound shot hit his own man, Ivanovic, before bouncing fortuitously back to him again. However, with the goal seemingly at his mercy, he dragged his effort wide, ensuring the spoils would be shared.