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Keogh scores winning spot-kick to set up tie with Accrington in round four
Saints led 2-0 through Armstrong and Redmond strikes
Wilson free-kick reduces the deficit before Waghorn heads in
Derby's Bryson earlier had finish ruled out by VAR for narrow offside call
Southampton 2-1 Derby
Danny Murphy
Former Liverpool and England midfielder on BBC One
Tom Lawrence has come over to the left. It looks like 4-4-2 now for Derby, with Nugent and Waghorn up top. They're going for it...why not?
#bbcfootball or 81111 on text (UK only)
Denham: There you go.. VAR allowing a goal for a minimal onside. Will that please the dinosaurs at all?
Oliver: If they are to review every goal with VAR the please don't use it. Kills the game and I feel Derbys first goal should stand
Here's the first goal of the night - Stuart Armstrong couldn't miss.
Southampton 2-1 Derby
Into the last 10 minutes. Derby send on Tom Lawrence for Tom Huddlestone...
Southampton 2-1 Derby
Danny Murphy
Former Liverpool and England midfielder on BBC One
That makes the last 14 minutes interesting.
It's been a good game, it's been intriguing...and it's not over yet
Southampton 2-1 Derby
There were four Derby players attacking that Harry Wilson free-kick, they all looked offside to me on first glance but again, it's tight margins. One defender's foot has played them all on and the goal stands.
Image source, AFPSouthampton 2-1 Derby
The goal stands!
Southampton 2-1 Derby
Danny Murphy
Former Liverpool and England midfielder on BBC One
It was a great ball in. I'm not sure whether it touched anybody. But let's wait...here we go
Harry Wilson
Game on!
We mentioned that Harry Wilson is a bit of a free-kick specialist, he whips in a brilliant ball, it's more of a cross than a shot but it runs straight through into the far corner.
Hang on - VAR...
Southampton 2-0 Derby
Into the final 15 miuntes. Jayden Bogle nutmegs Cedric and wins a free-kick right on the corner of the area. Soares is booked as Derby ready some subs.
Here they come actually. Jack Marriott is replaced by England goalscorer David Nugent...
A former Pompey player, he's booed on.
Southampton 2-0 Derby
Shane Long hobbles off, Sam Gallagher comes on.
Southampton 2-0 Derby
Southampton could well be setting the sat nav for Accrington in round four. But remember, Derby were 2-0 down in the first game too...
Southampton 2-0 Derby
Danny Murphy
Former Liverpool and England midfielder on BBC One
The finish was class but Jack Stephens coming out from the back - he was calm, powerful and made the right choice, playing the pass at the right time.
Redmond's made the difference. He's been a class above and deserves his goal.
Image source, ReutersNathan Redmond
That could well be that! A brilliant finish puts Southampton in firm control of this.
Just a quick pass through the middle, it catches Derby square and substitute Nathan Redmond has a clear run in on goal. Derby keeper Kelle Roos comes out, and Redmond just dinks it over his head and in.
Clinical. Again, there's a VAR check, but Redmond was onside. Goal is good...
Southampton 1-0 Derby
They still checked that on VAR. No idea why...
Southampton 1-0 Derby
Danny Murphy
Former Liverpool and England midfielder on BBC One
Southampton have done better in the second half, with Redmond coming on and the tactical change too.
Elyounoussi's been making more of an impact in the second half and it was good play by him.
It was unlucky for Long, he did the hard work, and it was a good follow-up by Armstrong.
Stuart Armstrong
The News at Ten may be saved! Southampton have a goal!
Good play from Shane Long as he first plays in Mohamed Elyounoussi on the right of the area, his cross picks out Long at the far post.
Again, he should probably score but his header is cleared off the line, and it pops up for Stuart Armstrong to nod home.
Southampton 0-0 Derby
Danny Murphy
Former Liverpool and England midfielder on BBC One
Redmond's made a huge difference since he's come on. That's what he gives you - great feet, the ability to manipulate the ball and get strikes off.
Southampton 0-0 Derby
Kelle Roos has had a very sharp game in nets for Derby. Saints sub Nathan Redmond skips inside a defender and gets a rasper away from the corner of the area and Roos has to make a big save at his near post.
Good work! Southampton on top in this second half. They've had 54% of play since the break.
Image source, ReutersSouthampton 0-0 Derby
I don't know if Harry Wilson will ever get a real chance at parent club Liverpool but he's clearly talented enough to have a really good career. The Wales international spins out of a challenge beautifully, hits an early strike with all kinds of swerve and Angus Gunn makes a comfortable enough save.
He can really smash a shot...