Manchester United manager Ruben Amorim put his first Premier League defeat since taking charge down to their set-piece shortcomings.

United were beaten 2-0 away to Arsenal on Wednesday, having initially held out through a goalless first half.

They were eventually undone by two corner routines, while the hosts came close to adding a third in similar fashion through Mikel Merino.

Amorim's side, meanwhile, failed to convert their own set-piece chances after seeing a Matthijs de Ligt header brilliantly saved by David Raya.

"The set-pieces changed the game, we could have been more aggressive towards the Arsenal box. Until the set-pieces, the game didn't have too many opportunities for both sides, the set-pieces killed the game," Amorim told BBC Match of the Day.

"They can put a lot of players near the goalkeeper and it's almost impossible to fight for the ball, but we have to manage to defend them and we already know we have to be better.

"We were committed and we lost to the set-pieces. If Matthijs can score in that moment, the momentum would be different.

"We tried to play, but they are a very organised team and it's hard to score. I felt the players were in control of the game, the set-pieces changed the game in the second half."

Manchester United defender De Ligt was in agreement with his manager, suggesting they performed well defensively aside from the goals conceded.

"In the defensive phase, the amount of chances we conceded without the set-plays [was good]," he told MUTV. "In the end, we played a little bit more offensive and conceded some chances at the end.

"But in general, we have to – and we will – offensively improve. We need to know what everyone is doing and we could have hurt them much more.

"We're still quite early with the new coach, but there are still positives. Overall, I'm really disappointed with the lack of points."

Their trip to the Emirates Stadium marked Amorim's fourth game in charge in all competitions. De Ligt is conscious that he has had little time and is sure improvements will come.

"We're on the road to improve as a team and I think the manager said it also. Maybe if we do it a certain way we have a bigger chance of getting results right now," he said.

"I think the way we are going now is obviously not perfect yet and everybody has to improve a lot and get used to the new system, but you can see certain things that are improving."