Manchester United manager Erik ten Hag has blamed injuries and a loss of concentration for their 1-0 defeat to Arsenal on Sunday.
It was the second successive defeat this week for the Red Devils.
Leandro Trossard scored the only goal at Old Trafford as the Gunners went on top.
Kai Havertz was kept onside by Casemiro and the German’s cross was converted by Trossard.
Ten Hag, who was without captain Bruno Fernandes and Marcus Rashford for the game, said afterwards: “Today we did. When you’re missing seven starting players, we are competitive with one of the best teams in the league.
“It’s about execution; when you don’t have the right attitude, when you don’t have the right press, it makes it easy for any opponent. That situation is a midfielder making a small mistake that has hard consequences.”