Erik ten Hag says Southampton's early missed penalty kick was the "turning point" in Manchester United's 3-0 victory at St Mary's Stadium on Saturday.
Ten Hag's men were level with the hosts through the first half hour when Diogo Dalot was judged to have fouled Tyler Dibling inside the penalty area.
Andre Onana subsequently saved the Southampton spot-kick, shortly before United went ahead via a Matthis de Ligt header, with the visitors in comfortable control from there.
"The start was not easy," Ten Hag told BBC Match of the Day. "I think the penalty was the turning point in the game.
"Not so far after, we scored and that was very important. From that moment on, the game was all ours."
Another important moment for United came in the 41st minute when Marcus Rashford scored his first goal of the season to double the lead.
The forward's struggles since last season have been well documented, but Ten Hag believes he could see better fortunes in that department now that he has opened his account.
"It's very important [for Rashford to score]," Ten Hag said. "For every striker, they want to be on the scoring list. Once the first is in, more is coming.
"Once a striker was talking about a ketchup bottle. Once it's going, it's coming more."
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