Matthijs de Ligt and Marcus Rashford scored shortly after Andre Onana's spot-kick save to put Erik ten Hag’s Manchester United on course for a much-needed 3-0 victory at promoted Southampton.Both sides returned from the international break in desperate need of a result as Saints sought a first point since their Premier League return against a team reeling from their humbling home loss to rivals Liverpool.Southampton started brightly but collapsed after Onana saved Cameron Archer’s poor penalty, with De Ligt’s first United goal and Rashford’s first of the campaign knocking the stuffing out of Saints.Alejandro Garnacho added late gloss to a win that alleviates some of the pressure on Ten Hag, who could ill afford to oversee the Red Devils’ first St Mary’s defeat since 2003 after back-to-back defeats.United began shakily but the game changed when De Ligt headed home two minutes after Onana stopped Archer’s spot-kick, with the striker then guilty of giving Rashford too much time to strike soon after.That period towards the end of the first half proved decisive on a day when captain Jack Stephens received a late red card for a foul on Garnacho, who scored in stoppage time.Saints boss Russell Martin made four changes on Saturday having largely stuck with the players that earned promotion, with homegrown Tyler Dibling among those brought in.The talented 18-year-old quickly showed United what they were up against, ghosting past Diogo Dalot at the halfway line, roaring down the right and then cutting onto his left to force Onana into a save.Saints looked sharp against initially cumbersome United, who took 15 minutes to find their feet and saw Joshua Zirkzee stopped from prodding in by home debutant Aaron Ramsdale.Noussair