It is a measure of how far Leicester City have fallen since their title triumph that, two goals down at half-time at St Mary's, there was not even a glimmer of hope that they would produce a stirring comeback.
What a contrast that was with this fixture last season, when they were trailing by the same scoreline, but stormed back to seal a point through a late brace by Jamie Vardy.
There was to be no storm this time, just a darkening cloud over the head of their manager Claudio Ranieri.
This was a day to forget for him, and for Vardy, too.
Having terrorised Southampton's backline here last season and flown to the top of the Premier League goalscoring charts in the process, the England striker was reduced to feeding off scraps, as Leicester were downed by goals from James Ward-Prowse and Jay Rodriguez, before a late Dusan Tadic penalty brought a sorry end to a miserable day.
The champions have now conceded more goals (37) this season than they did throughout the whole of their title-winning campaign.
Their fans may be looking forward to the next step of their Champions League adventure, but after this they must also be glancing nervously at the teams below them in the league table.
They sit just five points clear of the relegation zone, and Swansea's victory at Liverpool will only serve to tighten the knot in their stomachs.
"I tried to help my players in the last two matches and I changed our normal shape," said Ranieri, who watched his side fall to their second 3-0 defeat in a row after being dismantled by Chelsea last weekend.
"Against Chelsea I played with three defenders at the back. Today I played with a diamond in the midfield, and this provoked some misunderstanding. I made mistakes - it's my fault."
Despite Leicester's woes, credit must go to Southampton. This was a much-needed return to form after four straight defeats in the league, and it sets them up nicely for the midweek trip to Anfield for the second leg of their League Cup semi-final against Liverpool.
Having struggled to create chances for much of the season, they found some fluency and rhythm at last.
The only blemish on an otherwise rosy afternoon for their manager Claude Puel was a knock to star defender Virgil van Dijk, who limped off early in the second-half.
With club captain Jose Fonte having jumped ship to West Ham, it was the last injury Southampton would have wanted in this, the first of four games in the space of just nine days.
"We will see in the morning if we can have him for (the Liverpool) game," said Puel. "He's now our captain so it will be important to have him."
Southampton were dominant throughout. Against Leicester's narrow midfield diamond, the home side found particular joy down the flanks in the first half.
Two left-wing crosses presented Nathan Redmond with the first big chances, but his headed effort floated over the bar before a bobbled shot was then comfortably saved by Kasper Schmeichel.
There were also opportunities for Pierre-Emile Hojbjerg, who thrashed wildly off target, and Rodriguez, who headed wide, as the visitors afforded Southampton the run of both wings.
It was no surprise, then, that the opening goal was created down the sides.
This time it was the right, as full-back Cedric Soares burst into the clear before steering his cross towards the excellent Ward-Prowse, who swept a curling effort beyond Schmeichel and into the far corner.
"Since the beginning of the season he [Ward-Prowse] has made good progress," said Puel. "To see him scoring is very important for me."
Leicester had looked dangerous on the break through the whippet Demarai Gray, but they could hardly have begrudged Southampton their lead after a first-half spent largely on the ropes.
Southampton's second goal, though, would have stung. A Ward-Prowse free-kick from deep caused chaos in the box. Robert Huth could only nudge it into the path of Rodriguez, who lashed home from close range. If a single moment could encapsulate Leicester's fall from grace, it was this.
Bluntly put, it was not a goal they would have conceded last year.
Wes Morgan stabbed Leicester's best chance over the bar with around 20 minutes left and then, moments later, he turned the ball into his own net before his blushes were spared by the linesman flagging for offside.
That reprieve for Morgan was only brief. As the clock ticked down, he bundled over the substitute Shane Long in the box, allowing Tadic to rifle home an emphatic third from the penalty spot. (© Daily Telegraph, London)