Sunderland contributed to their own downfall with a comedy own goal from Santiago Vergini and another own goal from substitute Liam Bridcutt with further strikes from Graziano Pelle (2), Jack Cork, Dusan Tadic, Victor Wanyama and Sadio Mane completing the rout.
The defeat was the worst possible way to mark Gus Poyet’s 50th game in charge of Sunderland, while Saints continued their impressive start to the campaign as Ronald Koeman celebrated his manager of the month award in style.
Sunderland started the brighter of the two sides, but all their good work was undone after 12 minutes with one of the most bizarre own goals in Premier League history.
There appeared very little danger when Vergini tried to clear the ball from Morgan Schneiderlin inside the box only for the Sunderland defender to inexplicably volley his clearance past his own keeper and into the bottom with a strike a forward would have been proud of.
Things got worse for Sunderland six minutes later as Pelle celebrated his Player of the Month awatd with a tap in for his sixth goal of the season.
Steven Davis, who signed a new deal at Southampton earlier this week, was the creator as his perfectly weighted ball across the six-yard box was slotted home by the in-form Pelle.
Sunderland felt they should have been awarded a penalty on 35 minutes when Lee Cattermole played Steven Fletcher in on goal and he poked his effort on the stretch wide before being taken out by the onrushing Fraser Forster. The Sunderland players appealed for a penalty, but their claims were waved away by referee Andre Marriner.
Two minutes later and Southampton took full advantage of the penalty escape as Dusan Tadick picked out Cork’s run at the far post and he bundled the ball home despite Vito Mannone getting a hand on his shot.
Southampton almost grabbed a fourth goal just past the hour mark when Long unselfishly passed for Tadic inside the box and he poked his shot goalwards only to see Patrick van Aanholt get back and clear the ball off the line.
However, the home side did not have to wait long to make it 4-0 as Betrand got down the left and pulled the ball back for Pelle who saw his shot blocked by Mannone only for Bridcutt to get his feet in a tangle and bundle the ball over the line for another own goal.
The impressive Pelle grabbed his second of the game on 69 minutes when Tadic slipped him in on goal with a fine pass and the striker superbly swept his first-time shot into the corner past Mannone.
Sunderland gifted Southampton another goal on 78 minutes when Mannone’s wretched clearance fell straight to the feet of Tadic 25 yards from goal and the Serbia curled his shot into the empty net.
A minute later substitute Wanyama added a seventh goal as Tadic picked out the midfielder inside the box and he smashed a shot high into the past a demoralised Mannone.
The home side continued to pour forward in search of more goals and they made it 8-0 four minutes from time with the impressive Tadic again the creator as he pulled the ball back for substitute Mane to slot home and leave the home fans in raptures.
Phil Thompson’s verdict
“This was shocking, absolutely shocking. It was a shambles. People were not taking responsibility. Cattermole in midfield couldn’t get near anybody today. He didn’t have a leader. Nobody would stand up for the cause.
“This was astonishing. Yes, we can talk about the problems for Sunderland but it was brilliant for Southampton. This was players playing with confidence. We talk about the so-called big teams having full-backs pushing on, but this is how to do it; Clyne was going down the right-hand side and Bertrand down the left at the right times. They were passing the ball and interchanging – they are absolutely flying. This is where this 8-0 result happens. You’ve got one team playing to the top of their ability and the other one who have just been calamitous. That’s why you get this result.”