Ruben Amorim said he was forced to work with “time limits” on his players’ return from injury at Manchester United as he suffered his first defeat as the club’s manager with a 2-0 defeat at Arsenal.

Second-half goals from Jurriën Timber and William Saliba, both from corners, sealed the Gunners’ win and handed former Sporting CP coach Amorim his first league defeat in over a year.

But with the United squad still hampered by injuries and a lack of match fitness, Amorim said his selection continued to be affected by fitness issues.

Harry Maguire, Tyrell Malacia and Mason Mount all played less than an hour at the Emirates after recently returning from injury, while summer signing Leny Yoro made his first appearance for the club after a lengthy layoff with a foot injury.

“It’s not because I’m constantly changing, it’s because we have to make sure the entire team is fit,” said Amorim. “So for example, Harry Maguire has a time limit, Tyrell Malacia has a time limit, Mason Mount has a time limit, Leny Yoro has a real time limit, so within games we have to deal with different methods and different ways of playing with more meters to press.

“Tomorrow we have to assess whether the boys who are at some risk of injury will not play, so we have to get everyone working, playing and improving the squad.”

Despite the defeat, Amorim said he still took positives from his players’ performances at the Emirates.

“I evaluate the game regardless of the result,” he said. “As I said, you can take positive things from the 4-0 (win against Everton) but we have to improve and you already knew that.”

“But you can feel it in the stadium, especially at the end of the first half you can feel that they weren’t comfortable, you can feel it in the stadium, so you can take it.”

“You see a goal and then the momentum changes and it’s really hard for us to take full control of the game, but we’re trying.”

Amorim, meanwhile, said he would give Luke Shaw the time he needs to be fit after the England defender suffered another injury setback this week following a five-month layoff with a calf injury.

“What I can say since I arrived is that in the medical department he works a lot in the gym and on the pitch,” Amorim said. “We control the load during games, during training. He was losing weight, so he did everything.”

“If he continues to behave like this, he is a top player and we need him. No matter how long it takes him, I will be with him, we will help him return. Not only Manchester United, but also your national team needs a man like Luke Shaw, so we are here to help him.