The Red Devils failed to build on their midweek victory against RB Leipzig in the Champions League as Pierre-Emerick Aubameyang’s second half effort from the penalty spot inflicted Manchester United’s third defeat of the season.
Solskjaer’s men were flat and mustered up just one shot in the game before halftime, their fewest in a Premier League home game since October 2015, and had just three touches in the Gunners’ box, their fewest since December 2017.
“That's football for you. It goes up and down,” the Norwegian coach told reporters after the game.
"We didn't turn up, especially in the first half. That's what we have to address because we know these boys can be so good.
"We knew that this was the big game this week. And unfortunately in the first half we didn't play well enough.
"Second half we played better, we never seemed to have to defend too much. But when we did have to, we were too slow and gave away the penalty.
"The boy is running away from goal, there is no need to go for the ball. Not much of a touch, but it's probably a penalty.
"It's for other people to judge if we're making progress. We keep on working and we have another chance on Saturday against Everton."
Manchester United will look to atone for their sins when they travel to Turkey to face Istanbul Basaksehir at the Fatih Terim Stadium on Wednesday.
