Closing in on half time. Plymouth would have taken this I reckon, they are ending the half well with a lengthy spell of possession. The 'Oles!' are out now in fact as they spray it about.

Jay Rodriguez had a shot for Southampton, who remain the dominant side, but it's still all a bit sleepy at St Mary's. 

Image source, Getty Images

John Hartson
Ex-Wales striker on BBC Radio 5 live

Plymouth have responded really well after going a goal behind. They have not laid down, and they have not given up. They have gone close a couple of times.

David Melton: 0-1 I'm now sure this replay is all part of the Klopp masterplan, giving Coutinho & Sturridge valuable game time.

Ryan Lloyd: Why do we want to sell Lucas again? Let him stay until his testimonial at least! A wonderful player for the club.

Great chance for Plymouth! Oscar Threlkeld does brilliantly down the right to beat his man and fire in a low cross, it looks like a tap-in for Arnold Garita but Trent Alexander-Arnold recovers superbly to ghost in and clear it away for a corner!

Magnificent stuff from the young right-back. 

Image source, Reuters

A rare goal for Lucas here, a fine header from an excellent Coutinho cross but Plymouth may be disappointed to have fallen behind from a set-piece...

Yoann Gouffran hits the post with a brilliant improvised flick from Achraf Lazaar's cross from the left.

The hosts very much on top of a slow Birmingham so far.

Image source, Rex Features

The last time Lucas scored a goal, Ed Miliband was yet to beat his brother in the Labour leadership election. Quite literally a different world.

The home crowd want a red card out as Joe Gomez pulls down Jordan Slew as he tries to bustle through on goal - referee Graham Scott applies common sense and the rules of the game though and it's yellow. Slew wastes the free-kick.

The entire ground rises and conducts a minute's applause for Argyle fan Kevin May.

Image source, Reuters

David Cotterill tries it on again from 25 yards out and the Birmingham man flings a shot into the side-netting. 

Steve Claridge
Ex-Leicester striker on BBC Radio 5 live Sports Extra

Southampton keep trying the 'eye of the needle' ball. Get the ball wide, make the pitch big. Norwich are tucking the two wide players in and Southampton can get their wide players on the ball out there. But they keep playing it in the middle where Norwich are strong.

Mark Duffell: OMG Lucas has scored. When did that last happen? Collector's item. Remember where you were. 

Warren Wine: Can you believe it, Lucas scores, wow, seven years since his last goal, can he stay in the first team, we like a Brazilian.

Dave Carville: Plymouth now have to try something other than the 10-0-0 formation. What have you got? 

A shot on target! Southampton forward Josh Sims hits a drive from 15 yards which is tame and never likely to threaten too much but it is on target and Michael McGovern has to save!

Jonjo Shelvey has been afforded a remarkable amount of space by Birmingham so far and the Newcastle captain nearly makes them pay again, this time with a powerful shot from 30 yards that Adam Legzdins does well to parry out wide.

John Hartson
Ex-Wales striker on BBC Radio 5 live

Coutinho whipped in a corner, Lucas got a run in unmarked from the penalty shot and the ball flies into the roof of the net.

You can't say it has not been deserved. Liverpool have controlled the first quarter of the game. Lucas took the header well, but it was the pace on the corner from Coutinho.

Plymouth now have to come out and have a go at Liverpool.

Still no chances of note at St Mary's, it's very pedestrian. 

Plymouth will have to come out of their shell now - and they do instantly. Playmaker Graham Carey curls in a shot from a way out, Loris Karius only beats it down into the danger zone and a couple of men in green can't quite gather it in in time. That's got the home crowd roaring though. 

Image source, Reuters