Hasenhuttl's high-octane Saints spike Arsenal guns
Southampton 3 Arsenal 2
A breathless, relentless afternoon at St Mary's provided both a vision of the new Southampton and a glimpse of the same old Arsenal.
The Ralph Hasenhuttl era has its first major scalp, courtesy of a late Charlie Austin header, and the Unai Emery regime had its first unwelcome throwback to the final years of Arsene Wenger's reign.
As the rain began to pour down, Arsenal's new-found solidity and resilience were washed away along with their 22-match unbeaten record.
Three crosses and three headers were the downfall for the visitors, who found themselves largely outrun by a Southampton team who have embraced their new manager's high-octane methods.
Hasenhuttl started his Southampton career by promising to push his players "to their limits" in training, and here they stretched Arsenal like few teams have done this season.
The home side charged and harried for much of the opening hour, twice taking the lead through the predatory Danny Ings, and then showed the grit and character needed to survive the inevitable late pressure.
At the final whistle, a handful of Southampton players sank to their knees in the centre of the field, while St Mary's rose as one to herald what they hope will be a new era of optimism.
Meanwhile, Hasenhuttl grabbed his players in almighty bear-hugs after bounding onto the pitch in joy.
The German was in such a rush to celebrate that he forgot to shake Emery's hand. "I have to apologise," he said afterwards. "I had to run to my guys."
After starting his Southampton reign with a disappointing defeat to Cardiff City, this was early vindication of Hasenhuttl's methods.
For much of the first half, Southampton were everything that the former RB Leipzig manager would have wanted them to be.
Much like Emery alongside him on the touchline, Hasenhuttl is a devotee of relentless pressing, of a team squeezing and lurching around the field as one.
Southampton were on the front foot from the start, with Hasenhuttl celebrating a sliding tackle with a fierce fist pump as early as the fifth minute.
Austin's late header, added to two first-half strikes from Ings, secured Southampton's first home win in the Premier League in nine matches.
More significant than that, though, was the spirit they showed in fighting back after a pair of Henrikh Mkhitaryan equalisers for the visitors.
"With every ball win and every counter-attack, the belief was rising," said Hasenhuttl.
"To come back again and again was amazing because it showed we had the character to make the first step.
"It was a fantastic moment, very emotional. This is what I want to feel in the Premier League. This atmosphere after the game was special for me."
Hasenhuttl said the "fundamentals" are now in place for Southampton, for whom Ings tirelessly led the line. "He was very intense and he invested a lot," Hasenhuttl said. "When you invest a lot, you earn a lot."
The caveat to all this is that it was an understrength Arsenal team, whose defensive crisis was made worse by an injury to wing-back Sead Kolasinac in training on Saturday.
Granit Xhaka was therefore selected as a makeshift centre-back, while Laurent Koscielny started his first Premier League match after seven months out with injury.
The patchwork nature of the defence perhaps explains why all three of Southampton's goals came from crosses.
The first arrived after 20 minutes when Ings eased between Koscielny and Xhaka before meeting Matt Targett's whipped delivery with force.
On the touchline, Hasenhuttl's explosive celebrations carried him all the way into Emery's technical area, prompting him into a sheepish about-turn when the moment of passion had passed.
Arsenal responded well, despite Southampton's relentless pressure, and equalised shortly afterwards through Mkhitaryan, who headed home from Nacho Monreal's left-wing delivery, but they were again undone by Ings before the break.
This time, the cross came from the right and from Nathan Redmond, whose clipped ball was looped by Ings into Bernd Leno's top corner.
A calf injury to Hector Bellerin allowed Emery to introduce Alexandre Lacazette at half-time, and the Frenchman needed just eight minutes to pinch the ball off Oriol Romeu and set up Mkhitaryan for Arsenal's second equaliser of the day.
Hasenhuttl, clasping his hands to his face in disbelief, could only rue his luck as Mkhitaryan's shot deflected off Jannik Vestergaard's heel and trickled past the wrong-footed Alex McCarthy.
Southampton were denied a third by the offside flag after Shane Long had scrambled home from a corner, but they did not have to wait long for the decisive moment.
Long streaked down the right and crossed for Austin at the back post, who could not miss after Arsenal's Leno had flapped at the air. (© Daily Telegraph, London)