Russell Martin rung the changes, but of course there was one he didn't make and that ultimately cost us dearly, as a team that started brightly, faded badly without leadership or organisation.
Saints started brightly and for 30 minutes looked the better side, but then came the turning point of the match, Tyler Dibling who was playing without fear on his full Premier League debut, took on his man and was brought down for a penalty.
But who would take it ? no one in the crowd knew and it looked like the players didn't either, with usual penalty take Adam Armstrong on the bench, there wasn't one obvious candidate that anyone had seen take a penalty before.
Initially in looked like Ben Brereton Dias would step up to the plate, in the aftermath it looks like he should have been the man, apparently he has taken 7 penalties before and scored all of them.
But he seemed to be talked out of it by Cameron Archer, who it turned out had never taken one in his previous 126 game career before this moment.
He took an age to actually take it and when he did, it was a tame shot that was too close to the keeper and it was easily saved, the ball came back to him but his header was tame and straight into the keepers arms.
This was the turning point of the afternoon, you could feel the confidence drain out of the players and the fans in the stadium.
At this point we needed leadership, we needed a Captain who rallied his troops and organised them as United suddenly found their confidence soaring.
But we didn't get that, within 5 minutes United had taken the lead and it was yet another disastrous moment for our defence, no one can deny that it wasn't a great ball into the box, but our defence had moved up and it should have gone out for a goal kick.
But one man hadn't followed his team mates, Jack Stephens was caught day dreaming and two yards behind the rest of the team, it meant that it played on a United player who headed it across the goal and into the far corner.
It was soft, Jack Stephens is meant to be the Captain and playing as a central defender in place of the axed Taylor Harwood-Bellis he should have been holding the line, yet he was completely detached from his team mates, it was unclear just who should have been calling the line.
Now United were full of running and confidence, again it needed leadership for the remaining 10 minutes of the first half, but we were all at sea, in the 41st minute we cleared a corner, but we were far too deep and Markus Rashford had too much time and space to curl a shot into the far corner.
You felt that the game was now gone.
The second half saw Saints under pressure and it needed a few smart saves from Aaron Ramsdale to keep the deficit at only two goals and with a slight chance of a comeback.
Just after the hour mark we made 4 changes in 2 minutes and it smacked of desperation, when you have to make 4 changes at once, it shows you are getting things badly wrong.
The withdrawal of Tyler Dibling drew boos from the crowd, but in truth he was understandably starting to tire, it almost seemed that Russell Martin had accepted that the game was over when one of the changes was Ross Stewart, a man who has barely played in 20 months, not Adam Armstrong whose hard work would have been welcome, this was now a training game, the manager had accepted that it was lost.
With 10 minutes to go came the sending off of Jack Stephens, TV replays showed it was totally justified, it was a studs up challenge and it was rash, but the real question is why Stephens was making the tackle in the position that he was on touchline way inside the United half.
Taylor Harwood-Bellis came on to shore up the defence and we almost got away with it, if it hadn't been for those meddling kids with 20 year old Garnacho sweeping home an unstoppable shot from a pull back.
So it was in the end a rout, but where we surprised ? The issue has to be squarely down to the manager, who has stubbornly followed a tactic that only he can see value in, In truth it came down to what I banged on about last season, a lack of leadership, the Captain has to be one of your best players, not just in terms of his performances, but in the fact that he is nailed on regular in the starting line up in his position and he is steady and a leader of men.
Our Captain on Saturday is none of those things and that resulted in the chaos that ensued, a leader of men would have sorted out who was taking the penalty, he would have held the back line as a unit, staying back or pushing forward together in unison.
Russell Martin is in many ways a lucky manager, last season the change in how we played was forced on him due to Alex McCarthy being unable to play with his feet when he came in after Gavin Bazunu's injury.
Now Martin has another change forced on him with the one man whom he always picks being suspended for three games, the big question is will Martin still be at St Mary's when Captain Jack returns after suspension.
I will stick up for Jack though, he is in a position he should not be in, he is a good squad player, he has never been a leader and for that matter a regular starter in that many seasons, he is now getting the stick, he is not showing a lack of effort in his game, he should not have this pressure put on him.
But there were some plus points, Tyler Dibling was exceptional in the first half hour and should be one of the first names on the team sheet. Aaron Ramsdale made save after save and without him it could have been a lot more.
Aside from that it is hard to think of anyone who had a decent game, but after conceding those two goals we did show some team spirit to not completely collapse and that hs to be good news.
However it was just pure graft from certain players amidst chaos going on around them, there was absolutely no leadership from the bench or on the pitch.
The next game is now crucial and should we lose to Ipswich it is hard to see how Russell Martin will stay in the job.