Southampton 3 Newcastle United 1: Calamitous start proves costly with relegation beckoning
The club remains second-bottom of the Premier League and six points adrift of safety, with Crystal Palace having beaten 17th-placed Norwich City 1-0 at Selhurst Park.
Newcastle manager Rafa Benitez picked an attack-minded team at the St Mary's Stadium.
Benitez recalled Aleksandar Mitrovic and Ayoze Perez to his starting XI, but his side got off to a disastrous start.
Shane Long skipped past a series of United players, none of whom were able to challenge him, in the fourth minute before rolling the ball past Karl Darlow.
Benitez's side, backed by 1,762 travelling fans, struggled to keep hold of the ball.
And Ronald Koeman's hard-working side came back at them again and again, but their second goal didn't come until the 38th minute.
Daryl Janmaat slipped as he attempted to stop Dusan Tadic, who played in Long.
Long's touch found Pelle, who made it 2-0.
Janmaat then limped out of the game – he was replaced by Dutch countryman Siem de Jong – and Benitez took off Steven Taylor at the break and sent on Jamaal Lascelles for the second half.
But Victor Wanyama put the game beyond a reorganised United in the 55th minute.
Wanyama pounced after Darlow got his feet to a shot from Pelle.
Newcastle perked up, and Townsend tested ex-United goalkeeper Fraser Forster with a shot from 25 yards.
Forster was equal to that effort, but he couldn't stop the winger's 65th-minute shot.
Townsend took the ball on the right, cut inside and lashed a fierce left-footed shot past Forster.
But that was as good as it got for United, who take on Swansea City at St James's Park on Saturday knowing they simply have to take all three points.
SOUTHAMPTON: Forster, Martina, Fonte, Van Dijk, Bertrand, Wanyama, Clasie (Romeu, 77), Tadic (Rodriguez, 84), Mane, Long (Ward-Prowse, 60), Pelle. Subs not used: Stekelenburg, Cedric, Yoshida, Austin.
NEWCASTLE UNITED: Darlow; Janmaat (de Jong, 40), Taylor (Lascelles, 46), Mbemba, Anita; Townsend, Shelvey, Wijnaldum, Sissoko; Perez (Cisse, 70); Mitrovic. Subs not used: Woodman, Dummett, Tiote, Obertan.
Goals: Long 4, Pelle 38, Wanyama 55, Townsend 65
Referee: Robert Madley (Wakefield)
Attendance: 31,542 (1,762 Newcastle)