For around an hour, this was a barmy, breathless Cup tie involving two teams and their mutual disdain for taking a backwards step.
Twice already this season Southampton had left Manchester City wiping blood from their nose. Twice they had battled to parity. Here again, Saints marched on to the front foot and swung from the hip. It was a rousing watch.
And then, with the game perfectly poised at 1-1, City snatched it away. Three goals in 16 minutes sucked the life from St Mary’s.
Manchester City cruised to victory against Southampton in their FA Cup quarter-final clash on Sunday afternoon
Raheem Sterling (above) opened the scoring in the early stages of the game to give Manchester City the crucial lead
It was brutality laced with brilliance. There was a Kevin De Bruyne penalty, Phil Foden unleashed a sublime strike to make it 3-1. The fourth, three minutes later from fellow substitute Riyad Mahrez, wasn’t bad either.
And yet, this will sting for Southampton. Yes, City’s class and depth told. But this game turned on individual errors.
Saints got away with one from Jack Stephens in the first half because Aymeric Laporte decided to return the favour.
City weren’t so charitable after the break. Instead, after Mohammed Salisu needlessly fouled Gabriel Jesus inside the area, and De Bruyne scored from the spot, Pep Guardiola’s side moved through the gears.
Sterling’s (right) goal in the 12th minute of the game came after he was teed up by his team-mate Gabriel Jesus
The Saints managed to get themselves back into the game just before half-time when Aymeric Laporte scored an own goal
Another Salisu mistake allowed Foden to shoot. That’s now five FA Cup semi-finals in six seasons under Guardiola. So much for a blip; the treble is still alive.
‘How many times has it happened in this country? Once in this lifetime,’ said the City boss, as Liverpool now lie in wait at Wembley. ‘We are there for the titles and this is so nice, I would have signed at the start of the season to be in this position. We’ll see what happens.’
For Ralph Hasenhuttl, mixed emotions. Pride at how Southampton rattled City. But also frustration at what could have been. Even after Stephens gifted Raheem Sterling the opener, Saints were daring and dangerous. Even after they went 2-1 down, Che Adams saw a glorious chance saved by Zack Steffen.
Unfortunately the best teams only give you so many lives.
However, Kevin De Bruyne (above) restored Manchester City’s lead from the penalty spot after the half-time break
England international Phil Foden (right) extended Manchester City’s lead in the 75th minute – taking the scoreline to 3-1
‘We can be proud today for what we’ve done,’ said the Saints boss. ‘I haven’t seen so many teams play against Man City like we did today. This is very positive for me, it shows what we are able to do.
‘We had them on the back foot, but you must take your chances better than we did today. And don’t give them easy moments to score. And we did twice — this is not possible against this team. That’s the reason we lost.’
The die was cast early on. Twice in the space of two minutes the arc of this game bent City’s way courtesy of scuffs off Southampton boots. A third miscue — by Laporte — ensured a frantic first-half ended level.
That was probably about right. By then, Southampton had earned a bit of good fortune. Luck had deserted them earlier. First when Adam Armstrong was put through. His shot was badly struck and many behind the goal groaned before the ball reached the six-yard box.
But they didn’t know that the striker had hit it so poorly that the ball somehow veered back towards goal and on to the post.
Moments later, it was Stephens’ turn. The problem? His miskick came in a more perilous position.
The defender met De Bruyne’s cross inside his own area and tried to hook it clear. Alas, he barely made contact and fell over. That gifted the ball to Jesus who squared for Sterling to score via a deflection off Tino Livramento.
The goal should have given City control. Instead Southampton’s ambition was undimmed. Even if their finishing remained poor.Adam Armstrong fluffed another good chance; Shane Long missed a headed chance shortly before the break. Soon Hasenhuttl’s decision to leave Armando Broja on the bench looked unwise.
Especially given City were creating chances. The clearest came when Joao Cancelo’s devilish cross was turned on to the post by Ilkay Gundogan before Kyle Walker-Peters denied Jesus.
Turned out all this game needed was another blooper. Enter Laporte. When Mohamed Elyounoussi crossed low, Laporte diverted it into his own goal. City were furious, claiming offside.
Not even the break took the sting out of things. At one end, another brilliant Cancelo cross caused havoc. Salisu’s clearance fell to De Bruyne whose effort was cleared. He then turned fall-guy, allowing James Ward-Prowse to release Adam Armstrong in behind. His shot went wide.
With half an hour left, it was anyone’s for the taking. And then another blunder. Jesus was going nowhere but Salisu decided to intervene. ‘There’s no need to make the step. Clear penalty,’ Hasenhuttl conceded.
That prompted activity on both benches — Broja and Adams on for Southampton as Guardiola turned to Foden and Mahrez.
Hasenhuttl lamented how his changes failed to have the desired impact. City had no such concerns. ‘I would love to tell you that I am so clever and these substitutions happen, but this is not always the case,’ Guardiola smiled.
Salisu headed straight to Foden and he fired home from 20 yards. Then, after another ludicrous Cancelo cross, Mahrez beat Fraser Forster and that was that.
Riyad Mahrez added Manchester City’s fourth and final goal in the 78th minute to seal the victory over Southampton
Scroll down to re-live the action as it happened with Sportsmail’s live runner.
Three minutes of added time.
Riyad Mahrez drags a shot wide as he looks for his second.
Southampton make a couple more changes as Ibrahima Diallo and Will Smallbone come on for Mohamed Elyounoussi and Oriol Romeu.
Another one.
Cancelo uses the outside of his boot to cross it to Gundogan and he squares it to Mahrez on the right of the box. He knocks it around Salisu before slotting the ball low into the bottom corner.
A stunning strike.
De Bruyne clips it forward to Foden who rifles it into the top corner. Unstoppable.
Save!
Elyounoussi produces a great touch as he latches on to a long ball over the top. He squares it for Adams who sees his first time effort well saved.
Big chance.
Steffan enters the book for time wasting.
20 minutes to go. Unless the Saints can find an equaliser.
Frustration for the hosts. They had been playing well but that error from Salisu has undone all their hard work.
Substitutes for both sides.
Adams and Broja replace Long and Armstrong.
Mahrez and Foden come on for Grealish and Jesus.
The keeper goes the right way but De Bruyne’s strike is too good for him.
City back in front.
Salisu makes a foolish late challenge on Jesus just inside the area and the referee points straight to the spot.
Sterling runs at Livramento again, but the defender stands his ground to stop him from getting a sight of goal. It’s pulled back to De Bruyne instead, but he curls his effort over the bar.
Sterling tees up De Bruyne on the edge of the area but he hits it high and wide.
Almost a chance for City as Grealish finds De Bruyne in the box but he can’t sort his feet out quickly enough and the opportunity disappears.
Southampton looking much more confident now. They couldn’t have scored at a better time.
Armstrong with the first effort of the half but he pulls his shot well wide from the edge of the box.
City get us back underway.
Southampton equalise with the last kick of the half!
Stuart Armstrong plays in Elyounoussi, who times his run absolutely perfectly. Steffen comes off his line to force him wide, so he tries to pull it back across goal instead. It hits Laporte which takes it bouncing over the line.
Two minutes of added time.
Wide.
Armstrong rises highest to win a header in the box but he nods it well wide.
Close!
A ball is swung in from the right and Long almost reaches it at the back post. Just too much on it.
Another good move from City as Grealish finds space on the left and tries to slip in De Bruyne. He’s closed down before he can get a shot away.
Stuart Armstrong stays down after a cynical challenge from Cancelo. He’ll be OK.
Rodri picks up a loose ball in midfield, moves to within 25 yards of goal and hits a low drive that swerves just wide of the far post.
Salisu is down and receiving treatment now. He took a heavy landing after an aerial collision, but he slowly gets back to his feet and will be able to carry on.
Half an hour in and Manchester City have the lead and are in control but Southampton have had their moments. Better finishing and they could be level so City will want another goal.
Off the post!
City almost double their lead.
Cancelo knocks it past Livramento to take it to the byline before lifting it to Gundogan at the near post. He hits his shot against the woodwork from close range and Jesus can’t collect it on the far side.
Stephens flies in on Grealish and wins the ball but hurts the Englishman in the process. He stays down for a while before returning to his feet.
The game has slowed down a little since that goal. City looking comfotable.
De Bruyne picks Romeu’s pocket on the edge of the box and he quickly lays it off to Jesus. Salisu rushes out to him, forcing the Brazilian to take the shot quickly, and he fires it high over the bar.
A quarter of an hour into the game now. 76 per cent possession for City and the crucial goal.
Sterling gives City the lead!
Off the post!
Southampton almost take the lead as Adam Armstrong is played through and drags his shot across the keepper.
It beats Steffen but hits the post.
Chance.
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It’s Sterling again who receives the ball on the left hand side of the box before slicing his shot into the side netting.
Should have done better.
First effort of the game comes from Sterling, who cuts inside form the left and curls one straight into the keeper’s hands from the edge of the box.
City dominating the ball in the early stages, as expected. No openings as of yet.
Southampton get us underway.
Southampton boss Ralph Hasenhuttl, speaking to BBC Sport: “It is a good chance for the club to win something big and to win something big you have to beat big teams. A good challenge for us.
“Pep will find solutions and we will have to find answers for the solutions he has found. This is what football is about.
“We can play better than the last three games. We are positive we can do it.”
Southampton have only lost three of their past 18 FA Cup matches, two of which have come at the semi-final stage at Wembley.
They are also unbeaten in their last eight home games in the competition.
This is Manchester City’s fifth FA Cup quarter-final in six seasons under Pep Guardiola.
No team has scored more FA Cup goals than Manchester City this season.
City have only failed to score in two of their past 19 FA Cup games.
The draw for the last-four this afternoon, the semi-final draw will be made around 5:30pm on ITV, ahead of Nottingham Forest vs Liverpool.
And welcome to Sportsmail’s live coverage of Southampton vs Manchester City.
Team news to follow with kick-off at 3pm.
Spencer Morgan
Host commentator