The clans gathering on the south coast : Picture by @YTJourno
**Southampton (1) 2** Stewart 35, Charles 85
**Arsenal (0) 1** Gyokeres 68
For Saints, a memorable evening of utter joy. For Arsenal, only despair.
In the space of two games their ambitions for the season have halved. Two cup disasters leave them with the league and Europe to concentrate on now - with a whole load of self doubt as baggage to carry on drooping shoulders.
The imperious way Man City thrashed Liverpool earlier in the day will only accentuate the dread starting to course through the veins. The trip to Portugal this week will demand a serious response.
The writing was arguably on the wall from the very start. The Saints were in no mood to let this occasion pass them by - even if the Championship side's rush towards the play-offs has made their main objective for the season obvious.
They disposed of Fulham in the previous round and once again donned the famous yellow and blue kit they wore on their way to winning the 1976 FA Cup final against Man United. They were on a mission.
They are on a superb 15-match unbeaten run and their attacks were full of pace and confidence. They took the lead and found a winner late on after Arsenal had drawn level. No one would claim they did not deserve it.
It needed some last-ditch interventions from Gabriel to stymie the marauding Tom Fellows and Leo Scienza early on and there seemed danger in everything they did. .
That said, the Gunners almost took the lead when Gaby Martinelli's goalbound strike from just outside the box was headed behind by skipper Taylor Harwood-Bellis and Martin Odegaard sliced wide when he should have put away a Martinelli cutback. Kai Havertz's deflected shot did not miss by much.
Max Dowman was seeing plenty of the ball down the right too and rifled at Daniel Peretz from an acute angle.
But they kept looking vulnerable to the Saints breakaways that made for a thrilling spectacle and when James Bree floated a cross to the back stick, Ross Stewart made the most of Ben White miscalculating his leap to get the ball under control and rifle past Kepa.
Arsenal's response was frankly feeble and they almost fell 2-0 behind when Cristhian Mosquera's awful sideways pass gave Fellows a run on goal but the winger pinged over the bar.
Then, moments after a triple substitution from Mikel Arteta, Scienza curled a shot onto the top of the crossbar, with the Arsenal defence once more looking less than water-tight.
How to stop the unfolding nightmare? Finally the Arsenal found a way and after Havertz had burst into the inside left channel, his pull back was smartly put away by one of those three subs - Viktor Gyokeres.
It ought to have been a good omen, with the Swede having scored the winning goal for his country in the World Cup play-off win against Poland a few days ago. It was not to be,
Gabriel, who slid the ball through for Havertz to help set up the chance, went off with a knee injury, which must make him a doubt for the trip to Sporting for the Champions League on Tuesday. The hope must be that there is no longer term damage as the Gunners can ill afford to be without him over the coming weeks.
Dowman gave Peretz work to go and Martinelli spurned a chance as Arsenal appeared to be cranking up the pressure but it was to be a night for the Saints - with sub Shea Charles in the right place to profit from an attack built from the right that the Premier League leaders just didn't deal with.
Cue pandemonium at St Mary's. They have a Wembley semi-final to look forward to.
As "Que Sera" played out over the PA, the Saints players cavorted with the delirious fans in the stands. Their transformation under Tonda Eckert has been remarkable and they will believe they can repeat that amazing success of 50 years ago.
**Saints:** (4-2-3-1) Peretz - Bree - Harwood-Bellis, Wood, Manning (Quarshie 97) - Bragg (Charles 76), Jander - Fellows, Azaz, Leo Scienza (Edozie 71) - Stewart (Larin 70)
**Gunners:** (4-2-3-1) Kepa - White, Mosquera, Gabriel (Saliba 72), Lewis-Skelly (Calafiori 60) - Odegaard (Madueke 61), Norgaard - Dowman, Havertz (Zubamendi 79), Martinelli - Jesus (Gyokeres 60)