Image source, Getty Images

Former Southampton striker Kevin Phillips: "Sheffield United had some great chances and will probably be disappointed not to be 1-0 up at the break but you can't be too disappointed because Southampton are a Premier League side and they have shown that if you are sleeping, they will punish you and have had a couple of chances themselves."

Finally Southampton have arrived! A great chance as Shane Long does superbly to get away from Chris Basham, pulls the ball back for Sadio Mane but he can't get his shot on target from a very promising position under attention from Bob Harris. Best chance of the half though.

Image source, PA

Steve McClaren comes down from his seat in the stands and shares a friendly looking chat with Jose Mourinho. Didier Drogba is crouched down with the medical staff and Kurt Zouma, a lot of concern down there. This will be a lengthy stoppage as they treat the big defender.

Drogba trots over to the sidelines to update his manager.

Image source, AFP

Shane Long leads a swift Southampton counter after a Sheffield United attack breaks down and Bob Harris is taking no chances, going in with a tackle but ends up fouling the Southampton striker and is shown a yellow card.

Kurt Zouma looks a class act every time I've seen him. He is currently having medical treatment though, he looks sparked out as Petr Cech caught him on the follow through. A stretcher is called for.

It's early days yet, but...

Chelsea supporter Ari Bughoo says:, external Kurt Zouma reminds me of a young Marcel Desailly.

Image source, AFP

Robbie Savage laying down the law there! Derby continue to see plenty of the ball but they have nothing to hurt Chelsea with. Imagine taking Wilfried Bony out of the Swansea team and you'd get an idea. Lots of nice passing, lots of admirable movement - but they haven't laid a glove on Chelsea.

Petr Cech does then lay a glove on Kurt Zouma, flattening him as he punches clear a corner. Zouma is out cold.

Image source, Southampton

Southampton:, external 4,000 Southampton fans at Bramall Lane for tonight's game.

Robbie Savage
BBC Radio 5 live at the iPro Stadium

"Derby are not good enough to play out from the back against this opposition. Not once have they got up the park and had them on the turn, Chelsea press high because they know they can nick the ball off them.

"What would I say to the Derby players? I'd be hammering them: Defend, defenders! Let's get up the park and let's get in their faces.

"This is a cup tie against the Premier League leaders, there's 30,000 fans here and they haven't touched them yet - get up the park!"

Image source, PA

The Chelsea fans are in full voice, reminding anyone listening that they are indeed top of the league. A good response from the home crowd though, whose side have played fine. They've just been punished for the one mistake they have made and are now in the unenviable position of needing to score twice against this mean Chelsea side.

BBC Radio 5 live sports extra

Former Southampton striker Kevin Phillips: "I am pretty sure Ronald Koeman will be frustrated. I would want to see more from my top players, I would want Schneiderlin on the ball, Wanyama on the ball, Long looks like a lonely figure at times and Southampton need to do more here."

Southampton have two players booked in as many minutes as Nathaniel Clyne is shown a yellow for fouling Bob Harris as he tried to break into the area, before Sadio Mane is cautioned for a foul on Jamie Murphy. A bit of frustration setting in perhaps?

Excellent defending this time from Richard Keogh, timing his block to perfection to prevent Didier Drogba from sweeping Chelsea into a two-goal lead. Andre Schurrle's cross was pinpoint in its perfection, Drogba met the ball on the bounce but Keogh hurled himself in the way.

Cesc Fabregas is a glorious player to watch at times. After popping up just off Didier Drogba he retreats back into the 'quarterback' role and pings it 40 yards into the run of Drogba, over the top. The veteran's first touch is assured but a combination of Richard Keogh and Jake Buxton smother his shot and clear their lines.

Sheffield United win a free-kick in a promising position, pretty central and within shooting distance. Florent Cuvelier fancies it but floats the set-piece wide of Fraser Forster's goal. Moments later, Mark Howard fumbles a free-kick at the other end of the pitch, a melee in the area ensues and Sadio Mane manages to get a shot off, but can't put it on target.

Robbie Savage
BBC Radio 5 live at the iPro Stadium

"Don't try and play out from the back against opposition such as Chelsea. Richard Keogh is captain of his team, he plays for his country. He did it in last season's play off final as well, giving the ball to Bobby Zamora - get rid of it man!"

Derby just need to ride out the next few minutes. Chelsea's tails are up, they ping the ball around for fun as their fans enjoy themselves. Filipe Luis takes the opportunity to thrash in a left-footed shot which tests Lee Grant.

Chelsea fan Ian in Whitley Bay: Gutted I can't be in Derby tonight (never thought I'd say those words!) been to our last two quarter final matches away to Sunderland and away to Leeds. Leeds away is a memory I will treasure: Rafa getting stick from all four sides of Elland Road and singing "5-1, and even Torres scores!" How we laughed.

Image source, Reuters

So much composure! Chelsea lead through one of their star names, as Eden Hazard strokes the Premier League leaders ahead. It comes as Rams defender Richard Keogh makes a mistake, pressed on the edge of his box into giving the ball away, Cesc Fabregas feasts on the loose ball and instantly plays it into Hazard's run. Many players would shoot first time but he knows he can cut across Jake Buxton, he still then waits for Buxton to commit himself before drilling in a low finish. Classy stuff.

Image source, Reuters

Steve McClaren mentioned before the game the importance of getting through the opening 20 minutes unscathed, and his side have done that. They play some picturebook football at times but where are the goals coming from? John Terry and powerhouse Kurt Zouma look unflustered at the back for the Blues.