Ruben Amorim has explained how Manchester United will avenge their Premier League defeat against Arsenal when they return to the Emirates Stadium in the FA Cup third round. United made it difficult for the hosts on Wednesday night but were undone by two corners to suffer their first defeat of the Amorim era.

The Red Devils were blunt in attack, but the visitors' compact gameplan was working to perfection before Arsenal's sixth set-piece goal of the season in the 54th minute.

Jurrien Timber headed Declan Rice's pinpoint delivery past Andre Onana to send Mikel Arteta's side on a winning course.

Arsenal's seventh set-piece goal of the campaign arrived on 73 minutes when William Saliba directed the ball into the net after a corner from the other side.

The Gunners could have notched one or two more before full-time, but United stayed firm to limit the damage at 2-0.

Amorim and his players don't have long to wait before the opportunity for revenge comes around at the start of the hunt for a record-equalling 14th FA Cup.

Arsenal will host United again in round three between January 9 and January 13 after Mark Hughes and Dion Dublin drew the blockbuster tie at the start of Monday's draw at Old Trafford.

And Amorim made it clear that his side would have to improve their set-piece defending when they return to north London in just over a month.

"Set pieces. That is important," the Portuguese head coach responded to Amazon Prime Sport when asked what must improve in the rematch.

"And we have to be more aggressive near the opponent's box. But we have a lot to improve in all areas of the team."

Arsenal's threat at set pieces was no secret, and Amorim could only praise Arteta and his staff for making use of what has become a cheat code for goals.

"We have to understand that they have years of doing that," Amorim explained.

"Even when you are here for so long, you can see that Arsenal can change games like that.

"We tried to defend them with the space of two days to train but it's hard for every team to defend the set pieces of Arsenal.

The United boss added: "It's incredible, especially the way they change the games.

"Because sometimes they aren't dominating, and I think today you feel it in the game. It was really divided, no big opportunities, and then two set pieces change the game."