Finally, Erik ten Hag could enjoy a game without the kind of lingering sense of jeopardy that had stalked his Manchester United so far this season. Four games in Ten Hag cut an embattled figure and was on the defensive, but after an awkward opening half an hour, well-taken goals by Matthijs De Ligt and Marcus Rashford allowed United to run away with things with uncharacteristic ease. Alejandro Garnacho completed the scoring in style, lashing United’s third into the roof of the net in the 96th minute. Southampton did not muster a shot from the moment Cameron Archer’s rebound from a 33rd-­minute saved penalty ended up in the gloves of André Onana and, to make matters worse for the Saints, their captain, Jack Stephens, was shown a straight red card for a high challenge on Garnacho. Aside from Noussair Mazraoui being forced off with an injury and cramp setting in for others, this was a near-perfect day for Ten Hag, who introduced Manuel Ugarte late on for his United debut. On this occasion the smattering of full-time boos were not directed at the manager. Rashford’s speculative effort on the hour, with United coasting at 2-0, summed up how quickly the mood shifted. He took a touch to steady himself and then with a swish of his right boot whipped a thunderous shot towards the top corner, only for Aaron Ramsdale to push the ball over. That United required a Onana penalty save to inspire them to a victory at a team yet to register a point since promotion is perhaps indicative of their peculiar and confusing state. But eight minutes later United led 2-0 and from that point there was no way back for a Southampton team who had given the visitors an uncomfortable ride for the opening half-hour. Until De Ligt headed United in front they were slapdash. There was the seemingly customary questionable body language from their captain, Bruno Fernandes, and De Ligt, fresh from a nightmarish international break with the Netherlands, found himself firefighting in defence. Amad Diallo offered the hosts encouragement with a couple of undercooked passes. By the same notion that Southampton’s supporters jeered Russell Martin’s decision to withdraw Tyler Dibling 63 minutes into his first Premier League start maybe points towards their problems, and the Southampton manager was tuned into the frequency. “Tyler got cramp,” Martin said. “I didn’t want to take him off either, but he was struggling.” Dibling was replaced by Adam Lallana, once an academy youngster himself, as part of a quadruple substitution but Martin’s team struggled to regain momentum. The 18-year-old is the latest academy gem and as Saints supporters headed home Dibling was the overwhelming redeeming light from a fourth successive league defeat. He forced a fine early save from Onana after drifting inside Diogo Dalot and later earned the penalty. Dibling paused, slowing down Dalot, and then pressed play, the teenager whizzing past the United left-back. In his desperate attempt to keep chase, the defender tangled with Dibling on the perimeter of the penalty area and Stuart Attwell pointed to the spot. A couple of minutes later Archer stepped up to take the penalty but Onana saved a weak effort low to his right. The ball boomeranged back towards Archer but his header lacked conviction and looped into the gloves of the United goalkeeper. Then United’s supporters sang the name of Ruud van Nistelrooy, now a sidekick to Ten Hag, and everything was all right. Joshua Zirkzee saw a shot deflected wide via Ramsdale’s fingertips and United led from the subsequent corner courtesy of a well-worked routine. Christian Eriksen played it short to Fernandes, who floated in a cross. United were queuing up, Zirkzee lurking behind De Ligt, who twisted mid-air to generate adequate power on a placed header. A few minutes later Ramsdale saved from Rashford at his near post as United flew forward 3 v 3. Sixty seconds later Rashford gunned for the same corner and this time he found it, stepping inside Archer on the edge of the box before barrelling a shot home. From there United were in cruise control. Mazraoui rattled the side netting at the beginning of the second half and Garnacho garnished an eerily routine win in the final seconds. Dalot latched on to a weighted Casemiro pass at the byline and cut the ball back for Garnacho to fire in.