At the start of the week Saints supporters would have predicted that they would be taking on a Manchester United side whose confidence would be at rock bottom after a drubbing by Liverpool, a few days later and things have changed at Old Trafford.
On Monday morning things looked bleak for the Red Devils they were facing one of their most hated rivals in Liverpool and had a squad in disarray, but ahead of the match Erik ten Hag unveiled his latest signing Casemiro from Real Madrid and dropped a few high profile underperforming stars and the rest as they say is history.
So Saints will now face a United side brimming with confidence and with their new 70 million central midfielder making his debut.
Some would say it doesn't look good for Saints and they have a point, however there are some things still in Saints favour, firstly Casemiro has barely played this season, his only game time has been 90 minutes in the UEFA Super Cup & 7 minutes as sub in La Liga two weeks ago.
Hopefully he will be lacking a little match sharpness and we can capitalise on that.
Secondly although United won against Liverpool, they did so more on adrenalin than dominating the game. They started out like a train, but once they went a goal up they tailed off, in truth they played a Liverpool side in just as bad a run of form as United themselves who were full of mistakes and missed chances, add to that a little good luck for United such as when they hit their own player on the line with a botched clearance and the ball rebounded clear and you have to surmise they were struggling a bit in the final 15 minutes to hold on to their lead.
So the hope for Saints fans is that they have invested everything in the Liverpool game, a game where they pumped themselves up and that they won't be able to reach the same motivational levels at St Mary's.
United will be without Victor Lindelof and Facundo Pellistri with injury but that aside ten Hag should have a full squad to pick from
From that perspective Ralph Hasenhuttl is only missing long term injury Tino Livramento and on the plus side he has Romain Perraud back from injury and that is his one of his dilemmas.
The first question for Ralph is whether he sticks with the formation used at Leicester or reverts back to a back 3.
Most Saints supporters would vote for the line up at the King Power, but will he go for the starting line up or the one that finished the game (almost).
The first dilemma is whether Ralph sticks with Djenepo as left back or throws in fit again Romain Perraud, the Frenchman is more of a natural left back but has not played at all this season through injury, he is fit again now, but is he match fit.
Add to that Djenepo has improved with every game on the left, he doesn't deserve to be dropped so it is a difficult one for the manager.
Secondly it was the line up that played between the 70th and 888 minutes that won the game, Che Adams came on as a sub, so does he start this time after his run of 4 goals in two games and if so is it Sekou Mara or Adam Armstrong who drops out, for me i would leave Mara on the bench, he is still adapting to the Premier League and could well be best used as an impact player in a game like this.
Secondly does he start Stuart Armstrong, he came on for Adam Armstrong, so the question is does Ralph leave just one or both of the two strikers that started at Leicester or does he look in other areas to bring in Armstrong.
If he brings in Stuart then the only real candidate to be dropped would be Moi Elyounoussi.
It is a good headache for the manager to have though and although we are still a player or two light, we are still as strong if not stronger than we were at the same time last year, we know that this team can play as was shown in the middle of last season, we just need to hit a good run of form again.
So for me it is about keeping it tight, United will undoubtably be on a high from the win over Liverpool in the opening stages of this game, we have to give them nothing and then start to impose ourselves on the game.
If we do that we have a chance, we have to remind them through our own endeavours that their confidence is a fragile one, they started the season badly due to issues that won't be resolved just by the signing of Casemiro, a player whom they have paid £70 million for, but at 31 is worth perhaps half of that.
A good game is in store at St Mary's and it's a sell out crowd, if you have read social media in the last few weeks you would think that Ralph Hasenhuttl couldn't walk down Above Bar without a bodyguard, but the reality at the games is that despite a brief burst of abuse when Leeds went 2-0 up a fortnight ago, the crowd have stayed behind Ralph and seem willing to give him a chance to show what he can do now the financial shackles are off a little.
Manchester United are an example of how thinking just spending money or sacking managers is not a great philosophy, they also showed us on Monday how a pumped up crowd can drive a team to victory against the odds.
If we learn these lessons then we can come out of this game with all three points.