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Former Southampton striker Kevin Phillips: "That is a world-class save. I said in the first half I like to see free-kicks in-swung so that if people miss it it has a chance of going in. That is what happens but Forster's reaction is stunning, he has kept Southampton in the game."

Image source, PA

Brilliant, brilliant save by Fraser Forster keeps the scores level. Jamie Murphy's inswinging cross evades everyone in the box and looks to be creeping into the far corner but Forster reacts superbly to deny the effort. Xavi loves him,, external and it is easy to see why.

Derby's best chance! Chelsea just switch off and John Terry wit the mistake, he sells himself out at left-back and Johnny Russell gets away from him. Russell scampers away and picks out Will Hughes arriving at pace.

Hughes gives it plenty but Petr Cech was right behind it and pushes it clear easily enough. Lovely play from Russell though and that has reinvigorated the 30,000 or so in the stands.

In second gear, conserving fuel. That's Chelsea. Eden Hazard threatens to lift the tempo momentarily but for once his touch is poor.

Robbie Savage
BBC Radio 5 live at the iPro Stadium

"Chelsea look like they're in second gear at the moment. They've got the goal and they're cruising - epitomised by Nemanja Matic in the middle. They look like they can step it up when they want to."

Southampton are out in a more determined mood in this half and they have half a chance as Shane Long flicks a ball on and James Ward-Prowse directs a header on goal, but there is not enough power to worry Mark Howard in the Sheffield United goal.

Chelsea as comfortable as your dad in his favourite chair with a brew on and a good paper. Come and get the ball off us if you can.

There are reports that Kurt Zouma lost a tooth in that collision with Petr Cech. Some dental work required for the big defender.

Derby get us back under way at the iPro.

Image source, AP

Back under way at Bramall Lane. No goals in the first half but plenty of entertainment, what will the next 45 minutes have for us?

A reminder that tonight's League Cup quarter-finals could go to extra time and penalties.

Richard Keogh's mistake led to Chelsea's opener but he was the victim of a style of play. If Keogh had slammed the ball downfield, I'm sure his manager and supporters would not be too happy.

Robbie Savage
BBC Radio 5 live at the iPro Stadium

"They're doing a great job these stretcher bearers. Yes, they could have gone a bit quicker but it's important they don't slip, a few players have tonight, and they get there."

Six second-round replays are taking place in the FA Cup tonight - with some juicy prizes on offer.

None more so than at Huish Park where the winners between Yeovil and Accrington will tee up a tantalising home tie against Manchester United. Still goalless there after a tense first half.

Elsewhere, Tranmere and Oxford are drawing 1-1 as they battle for the right to face Swansea.

Rochdale and Barnsley are also ahead in their matches and are 45 minutes away from clinching ties against Championship sides Nottingham Forest and Middlesbrough respectively.

Want some FA Cup action? Here's some FA Cup action.

We will bring you any news on Kurt Zouma as and when we hear it. Back to matters on the pitch - how can Derby respond in the second half. They simply haven't looked capable of getting at Chelsea so far.

A somewhat different viewpoint...

Porl Thomas says:, external With the amount of players feigning injury these days is it any wonder the Derby stewards were slow to react?

There will be four minutes added on at the iPro after that injury for Kurt Zouma. Branislav Ivanovic hasn't played at centre-half for a while but he is a more than capable deputy.

Arsenal fan Matt Fallon says:, external Disgraceful by the paramedics walking slowly towards the injured Zouma. Fair play to those Chelsea players who dragged them.

Kurt Zouma is replaced by Branislav Ivanovic.

Image source, Getty Images

Kurt Zouma's name is chanted as he leaves the field on a stretcher. A sporting round of applause from all four stands. Let's hope the big defender will be OK.