Nathaniel Mendez-Laing became the second player from a promoted team to score twice at Old Trafford in the Premier League after Louis Saha for Fulham in August 2001. Mendez-Laing opened the scoring from the penalty spot for his third goal of the season in the 23rd minute and made it 2-0 in the 54th from Josh Murphy's assist after being left unmarked by United defenders.
United, which sacked manager Jose Mourinho last December and replaced him with former player Ole Gunnar Solskjaer, finished the season in sixth place with 66 points, 32 points behind champions Manchester City, failing to qualify for the Champions League.
"Today was not the problem, you can have all the possession and chances you want but we concede easy goals and not score at the other," Solskjaer said. "That is not where our challenge lies, we have a long and hard way to be where we want to be. It will take some time to close in on the top, we finished five or six points behind third, fourth, fifth and that has to be our aim. The top two teams have set a standard higher than before and we have to take up the next challenge."
Since former manager Alex Ferguson quit in 2013, United has been unable to secure the Premier League title. Manchester United forward Marcus Rashford had a header well saved by Cardiff 'keeper Neil Etheridge but United fans had little to cheer about apart from the performance of Mason Greenwood, the 17-year-old forward who became United's youngest Premier League starter.
"Mason Greenwood was brilliant, he was our best player by a mile and that says a lot about the kid," Solskjaer said.