Footballing momentum can shift on things as simple as playing the right team at the right time.

After six home league games in a row without a goal for Saints, the last thing they needed was another Swansea to turn up at St Mary’s – a team with discipline who are prepared to stick at a game plan, get men behind the ball and defend for their lives.

Thankfully for Saints, they played West Ham, a team who showed very little discipline, especially in the first half, and who always had half an eye on attack.

It was an important day for Mauricio Pellegrino, who must have felt he needed a home win after the opening day goalless draw with Swansea at St Mary’s.

He really needed the side to get something going, and to try and build some momentum and confidence in front of goal.

Thank goodness then for West Ham, a squad packed full of quality on paper but seemingly only sporadic cohesion as a team out on the pitch.

They still needed beating of course, the chances still needed taking, referee Lee Mason still had to have his helpful input, but to just have the opportunity to do just that was a blessing for Saints.

And now they have kick-started their season and given themselves a platform to build on.

With one Premier League game left before the first international break – that away to promoted Huddersfield – Saints can actually relax a bit. Pellegrino too.

He has had a baptism of fire walking into a squad low on self-belief in the final third and with a star player so desperate to get away he has handed in a transfer request. Also the owners of the club have changed in the few weeks since he arrived. What a whirlwind.

All Pellegrino wants and needs to really stamp his authority on the team and the club is wins, and as many as possible as quickly as possible.

He also wants to get the crowd behind him and the team, which means showing some clear dividing lines between his management of largely the same squad that Claude Puel had.

To the fans that means entertainment and goals.

It would have taken the harshest of critics to complain they were short changed for excitement and drama on Saturday.

Indeed, the serene and quiet life seemed almost desirable for a brief period when it looked as if Saints were going to squander a golden opportunity for three points.

That it came to that, that they needed a stoppage time penalty, and in fairness a few moments of fortune throughout the game to get there given they played against ten men for two-thirds of it, was perhaps a little concerning.

So, too, by Pellegrino’s own admission their struggles to deal with direct balls into the box.

But these are early days, and all that really matters is that they survived the test of character and found a way to get through it and get the job done.

After Marko Arnautovic fired wide Saints broke their home scoring duck after nine hours and 15 minutes when Manolo Gabbiadini and Nathan Redmond combined and the former finished off the move with a shot across goal into the bottom corner.

Arnautovic troubled Fraser Forster with a header before a pivotal moment in the game when the West Ham midfielder senselessly closed in on Jack Stephens and slammed an arm into his neck.

He was seething that Mario Lemina hadn’t been punished for leading with his arm in an aerial duel moments earlier that left Arnautovic writhing on the ground holding his face but it was little excuse – especially as Mark Noble got away with a bad challenge in the aftermath of that incident.

Referee Mason brandished the red card and West Ham totally lost the plot as Jose Fonte, looking a shadow of the colossus he was as a Saints player, hauled back Steven Davis to present Dusan Tadic with the chance to make it 2-0 from the penalty spot, which he did, albeit unconvincingly via the trailing legs of Joe Hart.

Saints looked to have the game in the bag with the Hammers looking ready to throw in the towel altogether.

However, Saints let them back into it seconds before half time as Michail Antonio turned Oriol Romeu outside the box and fired in a low shot that Forster did well to save, only to see Javier Hernandez react quickest to the loose ball to turn home.

That boost was all the encouragement West Ham needed to get their act together.

They were a far more resolute and determined side in the second half and looked as though they fancied it.

Saints breathed a sigh of relief as they got away with a handball in the area by Jack Stephens, while up the other end there was a lack of positivity.

Gabbiadini clipped the top of the bar with an effort from range while Tadic forced Hart into a save, but it was only a minor surprise when West Ham equalised on 74 minutes.

Richard Cresswell’s left wing cross picked out the head of Diafra Sakho. Forster made a good reaction save to turn it onto the underside of the bar, but again it was Hernandez who got to the loose ball first and produced a wonderful volley from close range for 2-2.

At that stage Pellegrino reacted and gave Saints more attacking tools.

It looked like it was too little too late as Redmond’s deflected shot hit the bar and Saints were continually frustrated.

But then Pablo Zabaleta tried to give Maya Yoshida enough of a nudge to disrupt his header at goal and Mason awarded another penalty, which Charlie Austin duly tucked away for a stoppage time winner.

A turning point? Only time will tell, but this is exactly what Pellegrino needed - a win, goals and a very different feeling for fans leaving the ground to that which they have experienced over the last five months.