Southampton 2 Manchester United 3

At the beginning and end United were a mess – but the result was determined by what happened in between those two spells, as a pair of predatory strikes from Anthony Martial and one from Juan Mata earned a victory that sent Louis Van Gaal's side up to second in the Premier League table.

There is no precedent for any teenager trying to justify an initial investment of over €50 million in his talent but Martial is going about it in expert fashion, his two sharp finishes on his first Premier League start taking his tally to three goals in two league appearances since his record transfer from Monaco. The French youngster radiated elegant menace whenever United could bring him into the reckoning, which was not quite as often as they would have liked.

On a bright afternoon on the south coast Van Gaal spent most of the match using his left hand as a sun visor but he may have been tempted to drop it down to cover his eyes completely during the first half-hour as events on the pitch made for grim viewing from a United perspective. Southampton were dominant in every department, the visitors unable to cope with the hosts’ power, pace and technique.

Ronald Koeman had suggested beforehand that Graziano Pelle's power could prove particularly useful against Daley Blind, whom Van Gaal chose to deploy at centre back, with Marcos Rojo replacing the injured Luka Shaw at left back instead.

As per the Southampton manager's prediction, Pelle bullied Blind from the start but that was certainly not the only duel that the hosts were winning: Matteo Darmian could not contain the tricky Dusan Tadic, while all of United's defenders, especially Rojo, were flummoxed by the elusive movement and deft trickery of Sadio Mane. James Ward-Prowse was ably serving his more advanced team-mates from midfield, with United seemingly unable to get a grip on the game.

Pelle outmuscled Blind wide on the right in the 19th minute before crossing for Tadic, who exchanged passes with Mane and then drilled a low shot wide from the edge of the area. One minute later Tadic left Darmian flummoxed and delivered a cross from the left that Rojo diverted behind before Ward-Prowse could convert from close range. United were reeling and it was no surprise when they fell behind in the 13th minute.

Mane began the move from deep, flipping a pass out wide to Ward-Prowse before dashing into the box and getting on the end of the winger’s cross. David de Gea saved the shot from the Senegalese but Pelle calmly stroked the rebound into the net.

Fragile at the back United were flat and ineffective going forward. Wayne Rooney, deployed just behind Martial on his return from hamstring injury, was presumably supposed to be playing a role similar to the one that Mane was fulfilling for Southampton but England's record goalscorer was barely visible.

Southampton were buoyant and nearly made it 2-0 just two minutes after opening the scoring. Mane again personified the difference in the team's demeanour by harassing the sluggish Chris Smalling into surrendering possession. Oriol Romeu slipped a pass through to Pelle, who turned past Blind and fired a low shot past De Gea but against the outside of the post.

With United looking meek, there was an air of desperation to the visiting supporters cries of “Attack! Attack!”, which were aired as early as the 22nd minute. Martial strained to head a cross from Mata over the bar in the 24th minute but United were generally showing little sign of being able to placate their fans until, suddenly, they drew level in the 33rd minute.

Southampton allowed an innocuous ball into the box to run to Mata, who, possibly from an offside position, helped it on to Martial. The striker duped Virgil Van Djik with a feint and then slotted into the net from eight yards.

That goal transformed the match. Southampton’s exuberance seemed punctured, whereas United played with renewed poise and assertiveness. The visitors took control in the deliberate, possession-based manner their manager demands.

Van Gaal replaced Darmian with Antonio Valencia at half-time both to spare the Italian from further tormenting by Tadic and to demonstrate his confidence that United would spend most of the second period on the front foot. He was right. But he hardly anticipated that Southampton would help.

Maya Yoshida, however, turned inadvertent assister to Martial just five minutes after the interval, stroking a casual back pass into the striker's path. The teenager finished like a seasoned marksman, wrong footing goalkeeper Maarten Stekelenburg as he rolled the ball into the net from 10 yards. Koeman had selected Yoshida at right back to subdue Memphis Depay; the Japanese had been successful in that regard this blunder undid that good work.

Southampton were not entirely deflated. Mane, who was showing why Van Gaal had been keen in the summer to add him to his list of expensive recruits, pressurised Blind into conceding a corner in the 59th minute and from Tadic's delivery Jose Fonte powered a header that would have brought an equaliser if not for a magnificent save by De Gea, who clawed the ball off the line.

This United side is not inclined to pummel opponents. Rather they seek to oppress them gradually. Occasionally they produce incisive flourishes, however, and one such burst led to them increasing their advantage in the 68th minute. Depay received an astute pass by Bastian Schweinsteiger before twisting wickedly past Fonte and firing a low shot off the post. The rebound came to Mata, who finished first time from 14 yards.

Four minutes from time, Southampton served a reminder of their qualities – and United’s frailties – when Mane crossed from the right and the unmarked Pelle headed into the net from eight yards.

The hosts piled forward in search of another equaliser but were denied by two more fine saves by De Gea.

(Guardian service)