Erik ten Hag borrowed Cristiano Ronaldo’s ketchup analogy as he predicted Marcus Rashford will go on a goalscoring run after ending his Manchester United drought in a 3-0 victory at Southampton. “Once a striker was talking about a ketchup bottle, once it’s going, it’s coming more,” said the Manchester United manager after Rashford registered his first goal since March. The 26-year-old had gone 12 matches in all competitions without scoring but doubled United’s lead on the south coast, six minutes after Matthijs de Ligt headed in from a short-corner routine. “It is very important for him,” said Ten Hag, who said criticism of Rashford after the 3-0 home defeat by Liverpool was overblown. “We don’t pay attention to what the outside world is telling [us], but it was too much negativity to him because he created two great chances, 100% chances in that game and also in other games. He was playing very well and deserved a goal. Then you get your reward. He scored a great goal and for his age, the number of goals he has is amazing, and I’m sure he will score many more goals. To get into the season for every striker it is so important to be on the scoresheet so you can build momentum, build belief and then more goals can come.” De Ligt scored his first United goal to open the scoring, which was capped by the substitute Alejandro Garnacho, though United also survived a first-half scare when the Southampton striker Cameron Archer saw his penalty saved by André Onana. Southampton were awarded the spot-kick after the 18-year-old academy forward Tyler Dibling, on his first Premier League start, was fouled by Diogo Dalot. “The start was not easy,” conceded Ten Hag. “The penalty was the turning point and not so far after we scored. From that moment on, the game was all ours.” United’s £42m summer signing Manuel Ugarte came on for his debut late on in place of Christian Eriksen, who was preferred to Casemiro as a midfield partner for Kobbie Mainoo. Ten Hag said Ugarte trained for only 20 minutes with his teammates on Friday after returning to Manchester from international duty with Uruguay. “He had two sessions, one before the break and one yesterday,” he said. “We were happy we could bring him on and show what he could deliver.” Southampton are pointless after losing their opening four matches of the season. Russell Martin, whose side travel to Everton in the Carabao Cup on Tuesday, acknowledged Archer’s miss was a pivotal moment. “We played really well for 30-odd minutes,” the Southampton manager said. “We looked the team that was most likely to score. Some of the football we played was great but we didn’t make the most of it and then we missed a penalty and it changed the whole energy of the game. “It completely deflated everyone. We have to learn from that and find a way to get back into the game. Unfortunately you have to learn through pain.”