The whistle is blown and Sunderland deservedly seal a place in the last eight of the FA Cup after Craig Gardner's wonder strike.
Larsson is booked for pulling back Rodriguez.
We will have a minimum of three minutes added time as Steven Davis' shot deflects up into the air and Ustari gathers.
Sunderland play the corner shot and try to keep possession but Saints win it and hammer it downfield.
Play is brought back and Rodriguez is booked for a late challenge on Cattermole.
Borini leads another Sunderland break and feeds Wickham whose shot is blocked for a corner.
They almost underline the fact when Colback breaks and feeds Borini but his low shot is parried by Kelvin Davis.
It's certainly not like Sunderland are hanging on and they are looking the more likely.
Shaw elects to shoot from 25 yards but blazes wide - it's desperation stuff from Saints now.
Wickham charges downfield and screws a shot wide from just inside the box when he had an unmarked Borini screaming for a pass to his right.
Back to that miss and it was was great play against between Steven Davis and Clyne and he put it on a plate for Lambert and it was easier to hit the net than it was to put it over as he did.
Sunderland's final change see Gardner replaced by Jack Colback.
Southampton's final change sees Sam McQueen handed a senior debut as he comes on for Lallana.
It gets even worse for Saints as Clyne presents Lambert a gift but he somehow puts it over from four-yards - how costly will that be?
What a chance and Lallana should have at least got it on target from 10 yards out.
Good work between Steven Davis and Clyne sees the right back freed and delivers a low cross to the near post that is met by Lallana but he can only put it wide.
It's a now a horrible day in the North East with a strong wind accompanying the driving rain which will not help Southampton's cause.
Sunderland's second change sees Marcos Alonso on for Dossena.
It's the home side looking more likely to add to their lead rather than Saints forcing an equaliser at this stage.
Sunderland respond and a good move works an opening for Larsson whose hits a clean shot bfrom 20 yards but it's straight at keeper Kelvin Davis.
Saints take a quick free-kick and Lallana crosses for Lambert at the far post but his header lacks power and it's an easy save for Ustari.
Wickham and Gardner try to link up on the edge if the box but Hooiveld clears. Larsson wins it back and Wickham is just unable to get on the end of his cross.
Still no signs of Southampton getting back into this match - the goal looks as though it has really knocked the stuffing out of them.
Borini tries his luck from 25 yards but it lacks power and rolls harmlessly wide.
Striker for a striker so Sunderland are certainly not shutting up shop at this stage.
Sunderland make their first change with Connor Wickham on for Scocco.
Shaw is penalised for handball giving the hosts a free kick. Larsson whips it in and it goes out for a goalkick with no one able to get a touch in the six-yard box.
Larsson takes and O'Shea gets a flick but Saints scramble it clear.
Good work by Shaw sees him close down and get in a tackle on Scocco but at the expense of a corner.
Sunderland are still looking dangerous on the break and perhaps will relish the fact that Saints will now push forward more.
That's two big names on for Saints so hopefully that does show that they will fight to get back into this game which is a positive sign for us watching it.
That change comes with Morgan Schneiderlin and Jay Rodriguez on for Guly and Ward-Prowse.
Saints have been flat after the goal and it's no surprise to see that they are about to make a double change.
Celustka plays a searching ball forward and it's just too far ahead of Gardner as he burst into the box.
Still the rain falls but the pitch is standing up with no problems at all.
Steven Davis is given time to line up a shot 25 yards out but he cuts across it and the ball was always going wide.
Sunderland have a free-kick on the halfway line but Larsson is then penalised for a foul on Wanyama.
Wanyama goes to ground after a challenge from Cattermole on the edge of the box but play is waved on.
Dossena finds space to get in a cross but hsi first-time effort is way too deep.
We'll now see the mindset of Saints - I'm sure their fans will see this as an opportunity lost if they go on and lose the game to what is in many respects a Sunderland reserve side.
What a fantastic strike from arguably the best player on the pitch so far.
Borini broke for the hosts and looked to have the lost the ball but it bounced kindly into the path of Gardner who smashed the ball home from just outside the box with the ball crashing in off the underside of the bar.
GOAL! Gardner gives Sunderland the lead with an explosive shot.
Southampton respond and Lambert chests the ball down for Lallana who jinks past a tackle but fires over from 25 yards.
Gardner is perilously close to unlocking the Saints offside trap but once again the flag is raised.
One interesting point is that the crowd is just over 16,000 - some 22,000 less than it was when the teams met in the league last month which is a sad state of affairs for this prestigious competition.
Sunderland get the second-half under way and neither side has made a change at the break.
We will have a minimum of one minute added time, but Sunderland can do nothing with a free kick and the whistle is blown.
Mosts of Sunderland's threat has come from set pieces but they have caused little danger for a well-drilled Saints defence.
Larsson whips it in but Hooiveld rises highest in a congested box to head it clear.
The resulting free kick comes to nothing but the hosts earn another one when Shaw fouls Scocco.
We have a delay as Borini receives treatment but it appears as though he will be able to carry on.
Steven Davis is booked for a foul from behind on Borini.
Steven Davis lets fly from the edge of the box but his effort is blocked by John O'Shea and Sunderland clear.
It was always going to take time for the game to settle with so many changes having been made to both line-ups but it has been a decent watch so far.
The visitors are stepping up the pressure as we approach the interval.
Wanyama jinks his way into the box but Cattermole does superbly to dispossess him.
Saints counter with Clyne down the right and his low cross misses two team-mates stretching for it inside the box.
Larsson deceives everyone by pulling it back to the edge of the box for Gardner whose shot deflects wide for a corner which is cleared.
Shaw is penalised for a foul on Borini and Sunderland have a free kick just outside the box.
Celustka's short back pass almost lets in Guly but keeper Ustari reacts well to punt the ball downfield.
Gardner goes to ground in the Saints box after tangling with Lambert, but it's only a goalkick.
Ward-Prowse takes a short corner for Saints and Clyne crosses but the hosts scramble it clear. Lallana wins it back and his low cross to the near post is gathered at the second attempt by Ustari.
Larsson tries to find the run of Borini but Shaw steps across to block.
Borini gets free in the box and his tame effort squirms under the body of Kelvin Davis and rolls just wide but the offside flag is again raised.
The visitors have carried the greater threat going forward but the problem is that their attacks have been few and far btween so far.
A good move by Saints sees Shaw dink a cross to the far post but Ustari does well to punch clear.
Great work by Cattermole by his own corner flag sees him turn away from Lallana twice before he works space to clear downfield to huge cheers from the home fans.
Larsson whips in the free kick on the angle from 30 yards but Shaw heads clear for Saints and evenetually it goes out for a goalkick.
Yoshida brings down Borini and it's the first booking of the game.
It's been little bursts from both sides so far but both look dangerous in the final third.
A strong run down the right by Gardner sees him try to pull the ball back for Borini in the box but Hooiveld makes a fine block.
A decent spell from Sunderland and the home fans have found their voices.
Emanuele Giaccherini then cuts in from the left but just as he is about to shoot from 20 yards Gardner gets in his way and they both end up in a heap on the floor.
Celustka gets in a dangerous cross that Saints scramble clear and are fortunate that it does not fall to Gardner on the edge of the box.
A decent opening but still not much goalmouth action t report apart from Ustari's excellent save to his right.
Dossena plays a long ball forward to service the run of Gardner who is amazed to be flagged offside.
Nathaniel Clyne has space to get in a cross but it's over the head of Lambert and the hosts clear.
The game has sprung to life in the last few minutes and despite all the changes these sides are certainly going for it.
Gus Poyet is furious and insists it was a foul and it was inside the box. Replays suggest it was inside but there wasn't too much in the collision.
Sunderland counter and Borini goes down after seemingly being bundled over by Shaw but play is waved on.
Saints attack again with Shaw down the left and his low cross is blocked by Ondrej Celustka at the expense of a corner which is punched clear by keeper Ustari.
Great move by Saints as Lallana spreads the ball wide to Lambert in the box and he heads down for Ward-Prowse arriving unmarked but his shot from 14 yards is smartly saved by home keeper Oscar Ustari.
Larsson takes it but it is headed clear at the near post - a real waste.
Gardner plays the ball into Scocco and his cross is blocked by Hooiveld for a corner.
Larsson tries to pick out the run of Borini in the box but Jos Hooiveld reads the danger and gets across to clear.
A cagey opening as the rain continues to fall in Wearside.
The hosts win it back and former Liverpool left-back Andrea Dossena puts in a deep cross but Saints keeper Kelvin Davis gathers unchallenged.
The hosts have a free kick down their right which is played into Nacho Scocco but his first touch is poor and he loses possession.
Seb Larsson is asked to chase a ball down the flank but is knocked off the ball by Luke Shaw and the hosts have a throw, but they lose possession and Sainst have a goalkick.
I'm not entirely surprised the hiosts have made sweeping changes, but I did think that Saints would have fielded their strongest possible line up with Wembley on the horizon should they win today.
Southampton get us under way and the Stadium of Light is far from being full today.
We have just had a minute's applause for England legend Sir Tom Finney who passed away on Friday at the age of 91.
"Curious to see the Saints selection today. Granted we do not seem to have a lot to play for in the league, but our attention seems still to be devoted to league points with six changes from the win at Hull. I still think this is the best Saints side for a generation and we have enough to get through this tie," says Clem Hardy.
Wins to nil have been the formula for success for Mauricio Pochettino's Saints, with each of their last four victories coming without conceding - a trend they are 11/4 to continue. Jay Rodriguez is a good price to open the scoring at 6/1 with Sky Bet having netted seven times in his last nine away games. Sunderland's Fabio Borini, who scored in the 2-2 draw between the sides last month, has been price boosted from 8s to 10/1 to score first.
Sunderland boss Gus Poyet makes nine changes as he attempts to find a way past Southampton and into the FA Cup quarter-finals. Only skipper John O'Shea and midfielder Fabio Borini survive from the team which lost 2-0 at home to Hull in the Barclays Premier League last weekend, and there is a debut for Argentinian striker Ignacio Scocco. Saints manager Mauricio Pochettino, who was sending out his team for the fourth time this term against the Black Cats, makes six changes with Kelvin Davis, Nathaniel Clyne, Jos Hooiveld, Victor Wanyama, Guly Do Prado and James Ward-Prowse replacing Artur Boruc, Calum Chambers, Jose Fonte, Jack Cork, Morgan Schneiderlin and Jay Rodriguez.
The teams are in and are as follows - Sunderland: Ustari, Celustka, Vergini, O'Shea, Dossena, Larsson, Cattermole, Gardner, Giaccherini, Scocco, Borini. Subs: Ki, Wickham, Colback, Mannone, Alonso, Roberge, Mavrias. Southampton: Kelvin Davis, Clyne, Yoshida, Hooiveld, Shaw, Steven Davis, Wanyama, Ward-Prowse, Do Prado, Lallana, Lambert. Subs: Schneiderlin, Fonte, Rodriguez, Cork, Chambers, Gazzaniga, McQueen.Referee: Mike Dean (Wirral)
Early start in the North East so I have to say good morning and welcome to our coverage of today's all-Premier League FA Cup fifth-round clash at the Stadium of Light between Sunderland and Southampton. The weather is not good but the game goes ahead and that will be a relief to both sides, as well as the Southampton fans who will have had an extremely early start to make kick off. I also covered the league meeting between the two sides on January 18 when Saints impressively swept into a two-goal lead after 31 minutes, only for Sunderland to hit back to earn a 2-2 draw so I'd be happy with a repeat of that. The Black Cats are still heavily embroiled in a relegation battle and athough they have the Capital One Cup final against Manchester City to look forward to next month, boss Gus Poyet admitted this week that he would prefer to lose today's game rather than draw and have a replay added to an already busy fixture schedule. Saints, on the other hand, are one of the few sides in the Premier League with seemingly little to play for in the final 12 games. They are clear of the relegation dogfight and are not likely to force their way into the top six so they can certainly give the FA Cup their undivided attention. Team news to follow and, as always, we welcome your views so send them to firstname.lastname@example.org and I'll publish the best ones.