That's it! Full time at St Mary's and United win 3-0 to book their place in round 4 and a date with Tottenham Hotspur!
Just a few minutes to go here. United still pressing, Saints defending stubbornly. Rooney has two shots but the first is blocked and the second is parried by Davis - he really has been great this evening.
Rooney looks odds on to score the fourth but Lancashire denies him with a great block!
Anderson shoots low and it's inches wide. He's still can't find that elusive first goal for United!
GOOALL! What was I saying about Saints keeping the score down? Rooney feeds Gibson who smashes it home from close range. Game, set and match.
Goal Darron Gibson
Rooney feeds Nani who closes in on goal and really should do better than cross it to a Saints defender. He had options there did the Portugeezer. The home side deserve credit for their second half display, they haven't given up and the fact United have only managed to score through a penalty says much.
United continue to coast, O'Shea volleys over and some fancy footwork by Berbatov looks nice but comes to nothing.
Free kick to United on the edge of the area after Berbatov is fouled by James. Nani takes but it flies over.
Yellow Card Lloyd James
More decent stuff by Rooney and Berbatov and the ball eventually comes to Gibson who blasts over. Rooney is trying to lift his team, playing cheer-leader at the moment.
Substitution Ryan Smith Lee Holmes
Berbatov to Rooney but Davis, who has had a fine game, comes out quickly to claim. It's one way traffic in this second half but the game as a contest looks to be over.
Rooney almost scores with his first effort! A good turn sees him clear on goal and although a defender gets back he manages to fire a shot which flies harmlessly wide.
Substitution Danny Welbeck Wayne Rooney
Some United possession results in a Nani scissor kick from a tight angle just going wide of the post. Some activity on the bench suggests that Wayne Rooney is about to make an appearance.
Darron Gibson has a run and shot just minutes after coming on, but it's high, wide and not particularly handsome.
Substitution Simon Gillett Morgan Schneiderlin
Substitution Oscar Gobern Kayne Mclaggon
Substitution Ryan Giggs Rodrigo Possebon
Substitution Michael Carrick Darron Gibson
Carrick just wide! He runs onto the ball on the edge of the area and fires a low shot wide of Davis' right hand post. Meanwhile, Saints are making a double change.
Chance for Southampton! Smith out muscles O'Shea down the right and then cuts inside and shoots but it's wild. That's a bad miss.
Welbeck goes down in the area after being sandwiched by two Saints players but the ref isn't interested. Referee Mike Riley is in the spotlight here. United's first goal looked clearly offside and the home fans are unhappy with that as well as the sending off and the penalty award to United. With the penalty they may have a point but the red card looked a decent decision.
Great save Davis! That should have been 3! Great work by Anderson down the left, he rolls it across to Welbeck who turns well and strikes it towards the top corner but Davies stops, again!
GOOAL!! Nani strokes home the penalty and United take a 2-0 lead!
Penalty Goal Nani
Penalty to United!! Nani takes a free kick which seems to hit a Southampton arm in the wall.
Welcome back to St Mary's. Southampton get the second half underway and immediately give the ball away to Nani who shoots well, well wide.
Half time at Southampton and United lead 1-0 courtesy of Danny Welbeck. The home side are not out of this yet but with a man down it will be a massive cup shock if they are to turn this one around. Can they do it? Find out after the break!
Great save Davis! Neville feeds Nani down the right and his cross is met by Welbeck at the near post but Davis does well to block!
Approaching half time at St Mary's and the visitors are in complete control. With a goal and a man down, Southampton have their work cut out!
Yellow Card John O'Shea
Nani tries to bend one past Davis but the keeper saves comfortably. O'Shea then bundles into Davis to prevent his throw out and is the next name to go into the book.
Yellow Card Rudolf Skacel
It's getting very feisty here at St Mary's. Nani is floored by Skacel who picks up a yellow card! The home crowd are not happy with the referee!
Paterson is sent off!!! The youngster goes flying into Vidic with studs showing and referee has no other choice than to produce the red card.
Red Card Matthew Paterson
Yellow Card Jonny Evans
The visitors are just knocking the ball around and keeping possession at the moment. Until Evans concedes possession allowing McGoldrick to steal it off him and the young defender hauls him down and goes straight into the book.
That should have been two! Great play by United, Berbatov sends Carrick through who looks certain to score but Perry gets back to block and the ball hits Carrick and rebounds to safety!
A free kick to Southampton is pumped into the box but Van der Sar claims easily. The Saints seem to have weathered the storm though.
Another good stop by Davis! O'Shea squeezes a cute ball through to Berbatov who plays it across the goalkeeper but he blocks! Southampton are hanging on a bit here.
Berbatov shoots low but Davis saves. It's all United since the goal. Can the Saints hang on in there?
A corner for United finds John O'Shea at the near post who flicks goalwards, goalkeeper Davis tips it onto the bar but Welbeck nods home the opener into an empty net from a couple of yards!
Goal Danny Welbeck
GOALL!! Welbeck scores and United lead 1-0!
Good save Davis! Berbatov tees up Nani down the left has and he shoots low but the Saints keeper dives low and parries the ball away!
Good spell for the Saints! Some neat work down the left sees Surman get to the byline and cross but United clear.
Anderson and Berbatov combine again and the Bulgarian plays an inviting ball into the box for Welbeck, but the youngester dallies and Surman blocks.
Anderson breaks down the right and finds Berbatov at the far post. He dinks a cross in but Davis claims, with a slight fumble. That's the best we've seen from the champions so far!
Southampton are pressing United back, who don't look completely convincing in defence. The hosts have been the better team in the opening 10 minutes.
Southampton make a couple of forays forwards, they've started confidently here. At the other end, Ryan Giggs breaks forward but his intended cross goes out for a goal kick.
United get the ball back and knock it around but neither team have got going yet, all a bit cagey in the opening minutes.
Here we go! United all in blue, get us underway but give the ball away and Southampton enjoy some nice, early possession.
Hello and welcome to goal.com's live coverage of today's FA Cup clash between Southamton and Manchester United. United bring a strongish side to St Mary's. Cristiano Ronaldo is rested and Wayne Rooney starts on the bench, however Dimitar Berbatov plays along with Ryan Giggs and Michael Carrick. Can Southampton pull off a cup shock? Find out here as kick off is coming right up!
Times In GMT
Live Final scheduled Suspended Cancelled Postponed