Three second-half goals from Southampton condemned Norwich to their fourth defeat in five games, denting their hopes of Premier League survival.
Saints top scorer Danny Ings curled in the opener shortly after half-time, before Stuart Armstrong doubled their lead five minutes later.
Norwich looked lacklustre at an eerily empty Carrow Road, and Nathan Redmond confirmed a win for Southampton against his old club when he slotted into the bottom right corner late on.
The Canaries remain bottom of the table following a 104-day absence.
And the time away from Premier League action, due to the coronavirus pandemic, did little to spark any signs of a comeback from Norwich, who have just eight games to claw back a six-point deficit on 17th-placed Watford above the relegation zone.
In the Premier League era, no team with 21 points or fewer after their 30th game of a season has survived the drop.
It was a positive performance from Southampton, who capitalised on the break, pressing high and taking advantage of space in behind the Canaries’ defence.
The Saints move up into 13th place, and have opened up a 10-point gap on the bottom three, having played a game more than those hovering around the safety mark.
Before the game, Norwich boss Daniel Farke said he believed five wins from their nine remaining fixtures would be enough to preserve their Premier League status.
But they remain five points from safety, with a goal difference considerably inferior to their rivals, and are still to travel to Arsenal, Chelsea and Manchester City in July.
This was a game against a side in the bottom half of the table which Farke would have been hoping to tick off as one of those five desired victories.
He experimented with their formation – starting Josip Drmic and Teemu Pukki up front together – but it did not pay off.
Pukki’s superb pass set up Drmic in the first half but the Swiss international looked rusty throughout and he needed a touch too many to get the ball out from under his feet, wasting the opportunity.
It was met with a faded roar from the new television-enhanced crowd noise – something that became a common theme in the first half as the hosts probed but ultimately failed to create many clear-cut chances.
And when Ings’ effort curled in, early in the second half, Norwich never recovered, conceding again five minutes later. They remain the only top-flight club yet to earn a point from a losing position this season.
Ings looks sharp on Saints return
When the Premier League kicked off in August, Ings was in top form for Southampton, netting 10 goals in his first 15 starts following a £20m move from Liverpool last summer.
But before the league was suspended, he had scored just once in seven games.
The break seemed to give him a boost because Ings came back looking sharp from the off.
He cracked the crossbar in the first half with a chance he would usually have buried, but he made no mistake second time around after the ball fell kindly for him in the box and he curled it past Tim Krul.
Moments later, he set up Armstrong for Southampton’s second.
The England striker’s energy did not fade in the second half as Southampton looked fresh and full of running – even the extra yards needed to fetch the ball in the absence of familiar ball boys and girls, did not affect them.
‘There is no way back’ – analysis
Conor McNamara, BBC Radio 5 Live commentator: “After this I don’t think Norwich are going to be good enough to stay in the Premier League. They had early opportunities but no composure in front of goal and then the belief just evaporated.
“Second half – I don’t think embarrassing is too strong a description.”
Chris Sutton, former Norwich striker on BBC Radio 5 Live: “Norwich are down, I don’t think there is any way back. It is the nature of the defeat too, Southampton were a different class.
“Where do Norwich go from here? It doesn’t look good for them, very, very difficult after this result to even contemplate staying in the Premier League.”
Man of the match – Danny Ings
Canaries can’t find the net – the best of the stats
Southampton recorded their biggest away Premier League win since beating Sunderland 4-0 at the Stadium of Light in February 2017.
They have taken 23 away Premier League points this season (W7 D2 L6) – only Chelsea (24), Man City (28) and Liverpool (37) have more in 2019-20.
Norwich have failed to score in six of their last nine Premier League games (W2 D1 L6), netting only three goals in that time.
Only Pierre-Emerick Aubameyang (17) and Jamie Vardy (19) have scored more Premier League goals than Ings (16) this season.
Norwich manager Daniel Farke has lost 19 of his first 30 Premier League games (W5 D6) – only Graham Taylor (21) and Mick McCarthy (26) have lost more of their first 30 games in the competition.
Armstrong has scored more Premier League goals in his last seven appearances (four) than in his first 44 (three).
Norwich welcome Everton – and the live BBC TV cameras – to Carrow Road on Wednesday, 24 June (18:00 BST), while Southampton host Arsenal the following day (18:00).