Match ends, Southampton 3, Newcastle United 1.
Southampton eased to a comfortable win over desperate Newcastle, who edge closer to Premier League relegation.
The Magpies were woeful and conceded in the fourth minute when Shane Long ran past a hapless defence and slotted in.
Graziano Pelle swept home the second just before the break and Victor Wanyama drilled in to make it 3-0 after Pelle's shot was blocked.
Newcastle barely threatened but earned a consolation through Andros Townsend's stunning strike.
The result leaves the Magpies six points shy of 17th place Norwich, who have played a game more, with six matches remaining.
Desperate times for the Magpies
It says a lot about Newcastle's fans - many travelling more than 330 miles - that they applauded their side off after yet another insipid display.
They provided the only solace for the players, who slumped to their ninth successive away defeat. Rafael Benitez's side now have six games remaining to preserve their Premier League status. With four of those games at home, it is possible, but not even their passionate supporters will be confident.
Newcastle went into the game having only twice won at Southampton in 16 league attempts. And after just four minutes they looked set for a fourth successive loss at St Mary's when Long drifted past weak challenges from Vurnon Anita and Steven Taylor to open the scoring.
Anita was playing out of position at left-back, while neither Chancel Mbemba nor Steven Taylor impressed at centre-half.
The best of the defensive bunch, Daryl Janmaat, slipped and injured himself in the build-up to Pelle's goal before Mane exposed further frailties on Newcastle's left side after the break, resulting in Wanyama's strike.
Is there hope?
Yes, but the defence has to improve markedly. Under Benitez's short tenure there had been initial improvements, but Newcastle have now conceded six goals in two games.
The saving grace might be the attack. There is enough firepower through Aleksandar Mitrovic, Giorginio Wijnaldum and Andros Townsend.
Townsend, who signed in January, scored a peach of a goal, having gone close moments earlier. Sadly for the Magpies, it came when they 3-0 down.
How good were Southampton?
Good, but they probably only reached third gear. They pressed the Newcastle defence from the whistle, knowing that they could force a mistake.
Long troubled the backline with his pace, while Pelle pulled both Mbemba and Taylor - who was substituted at half-time - out of position.
Jordy Clasie was once again tireless in his closing down, with Newcastle playmaker Jonjo Shelvey failing to impose himself on the contest.
The Saints are within spitting distance of a European spot and they will assisted by the long-awaited return of Jay Rodriguez. The England forward made his first appearance since October after recovering from foot surgery.
Man of the match - Graziano Pelle (Southampton)
Southampton manager Ronald Koeman, speaking to BBC Sport: "The performance was not everything I wanted, because I think in the second half, we had to score more goals. We created good chances. The key to winning was how we started, with a good spirit and a high tempo.
"It's all about how you start the game. We know the situation of Newcastle. If you give them the belief at the start, it can be very dangerous. A fast goal gave us the boost to continue. There was good movement and good goals.
"It's fantastic to see Rodriguez back, first of all for the player. He worked very hard to come back. It's up to the manager to give him that game time. He will be a very good player us in the future for us. It's important for Jay to get that game time to improve. That will not happen in one or two weeks. You need more time for that."
Newcastle manager Rafael Benitez, speaking to BBC Sport: "To be fair, the last three games have been the same. I've been saying the same thing. Second half we did much better but I'm really disappointed with the first half. Everyone needs to know that we have a lot of people behind us and so we need to give everything.
"Normally when you are in the position we are in, when you start the game conceding a goal, it's not the best.
"We have to show more character like we did in the second half. We have four more games at home and we will need everyone's support there. In the second half, the team showed we had character.
"It important that everybody continues to believe. The anxiety is killing us sometimes. If we can control these things then things will change."
The facts you need to know
- Pelle has been directly involved in seven of Southampton's last eight Premier League goals (four goals, three assists).
- Newcastle have lost their last nine away league games, their longest such run since May-October 1977.
- Ronald Koeman's side have won six of their last eight Premier League home games (D1 L1).
- The Magpies have shipped at least two goals in seven of their last eight Premier League games against Southampton.
- Long scored his eighth Premier League goal of the season, equalling his best haul in the competition (2011/12, 2012/13 with West Brom).
- Newcastle have conceded three or more goals in 10 Premier League games this season, a joint-league high with Aston Villa.
Newcastle host Swansea next Saturday and Southampton are away at Everton on the same day.
- 6José Fonte
- 17van Dijk
- 4ClasieSubstituted forRomeuat 77'minutes
- 7LongSubstituted forWard-Prowseat 60'minutes
- 11TadicSubstituted forRodriguezat 84'minutes
- 2Cédric Soares
- 22JanmaatSubstituted forde Jongat 40'minutes
- 27TaylorSubstituted forLascellesat 45'minutes
- 17PérezSubstituted forCisséat 70'minutes
- 10de Jong
- Robert Madley
- Shots on Target
Second Half ends, Southampton 3, Newcastle United 1.
Graziano Pellè (Southampton) wins a free kick in the attacking half.
Foul by Siem de Jong (Newcastle United).
Offside, Newcastle United. Siem de Jong tries a through ball, but Aleksandar Mitrovic is caught offside.
Attempt missed. Oriol Romeu (Southampton) header from the centre of the box misses to the right. Assisted by Graziano Pellè.
Cuco Martina (Southampton) wins a free kick in the defensive half.
Foul by Papiss Demba Cissé (Newcastle United).
Attempt missed. Oriol Romeu (Southampton) right footed shot from the right side of the box misses to the right following a corner.
Attempt blocked. Victor Wanyama (Southampton) left footed shot from outside the box is blocked.
Corner, Southampton. Conceded by Vurnon Anita.
Substitution, Southampton. Jay Rodriguez replaces Dusan Tadic.
Foul by Ryan Bertrand (Southampton).
Andros Townsend (Newcastle United) wins a free kick in the defensive half.
Foul by Virgil van Dijk (Southampton).
Andros Townsend (Newcastle United) wins a free kick on the right wing.
Victor Wanyama (Southampton) wins a free kick in the attacking half.
Foul by Papiss Demba Cissé (Newcastle United).
Substitution, Southampton. Oriol Romeu replaces Jordy Clasie.
Attempt missed. Sadio Mané (Southampton) left footed shot from the centre of the box is close, but misses to the left. Assisted by Graziano Pellè.