Teenager Marcus Rashford scored twice and set up the third as Manchester United derailed Arsenal’s Premier League title challenge at Old Trafford.
Rashford, who scored twice on his debut against FC Midtjylland on Thursday, steered in a loose ball for the opener then headed in three minutes later.
Ex-United striker Danny Welbeck nodded Arsenal back into the game, but Ander Herrera curled in Rashford’s lay-off.
Mesut Ozil’s volley gave third-placed Arsenal hope, but United held on.
Arsenal – who have not won the title since 2004 – remain in third place, five points adrift of leaders Leicester having now played the same number of matches.
The Red Devils moved back into fifth position with their first win in three Premier League games.