Both sides rung the changes from Saturday but ultimately Saints second string was better than Albion's although we left it very late.
Mark Hughes made 10 changes to the side that started the game against Leicester on Saturday the only survivor being Moi Elyounoussi who presumably needed the game time.
But it was still a strong side for Saints and the three new signings aside only Matt Targett wasn't a first choice player for Saints at some point last season.
The first half was awful though and was littered with poor defending from both sides when the whistle went for half time penalties loomed and there were still 45 minutes to play.
But Saints had looked the better side, Brighton had plenty of bluster as you would expect from a team of fringe players looking to push their way into Chris Hughton's plans for the rest of the season, we though had the experience but too much tendency to try and play the intricate balls that weren't coming off.
As the second half went on though you felt that if there was to be a goal then it would be Saints who scored it, with 20 minutes to go Mark Hughes made a positive substitution bringing on an attacker in Sam Gallagher and taking off Romeu, at least he was trying to win the game.
In fairness to Gallagher he changed the pattern of the game, his running seemed to unsettle the Brighton defence and he created several chances for himself and others.
With 10 minutes left there was no doubt that Mark Hughes was going for the jugular, off went Armstrong and Gabbiadini and on came Redmond and Austin and both started to hammer on the door for Saints.
Perhaps the best chance for a winner came just before it did, Button in the Brighton goal should have cleared a back pass easily but got spooked by Gallagher and fell over, Gallagher got the ball but the angle was too tight for a shot himself so he laid it back for Charlie Austin who from the penalty spot area hit a tame shot that was cleared off the line.
But with two minutes to go Saints won the game, Redmond did some good work on the left before getting to the byeline and pulling back a perfect cross for Charlie Austin to power home a header giving the keeper no chance.
All in all a win is a win and it will not only help our confidence but give us the chance of another run in this competition, but what can we take from it ?
The truth is very little, Brighton dd not seem interested in this game, Chris Hughton had made only one substitution when the winner went in and showed no real signs of trying to win the game, this was not the test that it would have been in the League .
It will have shown Mark Hughes he has options though, Matt Targett looked good at left back and Angus Gunn did little wrong in goal, Sam Gallagher's running was positive and changed the game but is he good enough in the Premier League.
Nathan Redmond looks to have found some of the confidence knocked out of him over the past 18 months, but Hughes problem is that whilst he has a big squad, few of them have yet to step up to the plate consistently, if they do that there will be no problems this season.
However you felt that Hughes team on Saturday at Crystal Palace will be a lot nearer the one that faced Leicester than the one that beat Brighton. No one who came in last night looked like they offered a better option than those who played at the weekend at least not in the starting line up.
But a victory is a victory and we are in the next round of the competition, it offers us a chance of glory this season and that is what football is all about, for Saints we need to be looking at winning a cup and the FA Cup is fast becoming the preserve of the Big Six, so if we want a trophy and Europe then it is the League cup we need to take seriously.
Certainly Saints supporters did with well over 2,000 in the crowd of 13,651 and it was they who made all the noise.