Southampton are first to every ball now. They win a succession of 50/50 tackles before Branislav Ivanovic fouls Dusan Tadic to give Southampton a dangerous free-kick on the left.

A penny for the thoughts of Jose Mourinho. He can have no complaints. Southampton have been asking questions of the Blues and they have had no answer. 

The Chelsea boss responds to the Saints' second goal by sending on Pedro for Willian.

Now then. This is a big moment. Radamel Falcao gets past Jose Fonte in the box and tries to get to the ball ahead of the diving Maarten Stekelenburg. He appears to do just that before tumbling over the keeper's frame. Falcao's feet definitely came into contact with Stekelenburg's shoulders, but was that purposefully done by the forward? The referee thinks yes and books him for a dive.

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Oscar looks to get the Blues going again with a cross towards Radamel Falcao at the back post, but Ryan Bertrand gets his body between the striker and ball and provides enough of an obstacle to ensure the ball drifts harmlessly out of play.

Southampton are feeding off Chelsea's uncertainty and nervousness. The men in red and white are hunting in packs, causing errors and look dangerous every time they pour forward.

Chelsea need to dig in or this evening could get even worse for them, when what they desperately need is for it to get much better.

Image source, PA

Blues fans are voicing their opinions on who is at fault for Chelsea under-performing this season...

Jamie Jennrich: Really need to drop Ivanovic, his sloppy pass lead to the foul which led to the goal - enough is enough.

Shohidur Rahman: Don't get Koeman's tactics. Giving Ivanovic a free ride. Why not put Mane on that side?

Lifa Nati: Chelsea will lose because Mourinho continues to play the same under-performing players. Fabregas being one of them.

Get involved with your comments on today's matches on Twitter #bbcfootball, external, on text 81111 and via the BBC Match of the Day Facebook page., external

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There's no hiding place for Mourinho as Southampton start the first half on the front foot. The perspex dugout isn't shielding Jose from his side's performance

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Three big chances for Sadio Mane to put Southampton ahead in the space of a minute. The first is a sliding finish, set up by a lovely ball for Dusan Tadic into the box, but denied by a good save from Asmir Begovic. The second and third are efforts from deep in the box, both blocked by a Chelsea defender. James Ward-Prowse ends the attack by firing wide from 20 yards.

Chelsea are hanging on by their fingertips.

Image source, Opta

Ramires has paid the price for a disappointing half in which he struggled to make an impression. Most of his forward passes were unsuccessful (red arrows).

The players are back out. Big 45 minutes coming up.

Both teams have made a change. James Ward-Prowse for Oriol Romeu for Southampton, probably because the latter had been booked.

Nemanja Matic is on for Ramires, probably for the same reasons.

Jose Mourinho had a point when he referred to this as his worst spell in management. They have conceded as many Premier League goals this season as they did in all of Jose Mourinho's first season as manager in 2004-05. 15 in total and counting. 

In addition, they have kept only two clean sheets in 12 matches this campaign in all competitions.

It started so well for the struggling Blues with Willian's opener. But they have a real game on their hands now thanks to Davis' leveller. It could have been worse as well, with Southampton having two good penalty shouts turned down.

Jose Mourinho needs a big half-time team-talk if he is to conjure up a result to end the 'worst spell of his career'.

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For once, Willian's free-kick skills let him down as his set-piece (given for a foul on Oscar 25 yards from goal) strikes the wall. That will be the last act of the half.

Sadio Mane is fouled again by Ramires, who seems to have overstepped the line once too many.

Oh, what a chance for Ryan Bertrand, who is given a clear sight of goal by Sadio Mane's superb ball into the box only to be denied by the onrushing Asmir Begovic. It is a very good save, but the former Blues defender should have done better with his finish.

Image source, Reuters

Much to the delight of the Southampton fans, Graziano Pelle is awarded a free-kick for a foul by Gary Cahill 40 yards from the Chelsea goal. 

The away side are close to turning the ironic cheers into legitimate ones as the free-kick is steered back across goal by Virgil van Dijk before Gary Cahill puts it behind. After the initial corner is cleared, Sadio Mane's deflected return has to flciked behind by the diving Asmir Begovic. A second corner comes to nothing.

Nervous times for Chelsea.

Image source, Reuters