Ruben Amorim has warned his Manchester United players “the storm will come” and there will be difficult times ahead despite a promising start to his tenure, as his team prepare to face Arsenal. The 39-year-old is unbeaten in his opening three matches as head coach, winning twice, but the trip to the Emirates Stadium on Wednesday night pro­mises to be a tougher challenge.

“The storm will come,” Amorim said. “We are going to have difficult moments and we will be found out in some games. And I know that because I know my players and I know football and I follow football.

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“I understand the difference between the teams and we are in the point in that we are putting simple things in the team, without training, and you feel it in [last Sunday’s] game against Everton: they changed a little bit the way they were building up. They are a very good team, and we had a lot of problems because we cannot change it by calling one thing to the captain. We don’t have this ­training, so let’s focus on each game, on the performance, what we have to improve, trying to win games.

“I know it’s really hard to be a Manchester United coach and say these things. We want to win all the time, no matter what, we are going to try to win, but we know we are at a different point, if compared to Arsenal. We go with confidence to win, but we know we need to play very well to win.”

United will be without Luke Shaw after sources confirmed the defender is expected to be out for a few weeks after a fresh injury setback. “I’m devastated and it’s extremely tough to come to terms with reality at this moment in time,” the player stated on social media on Tuesday night.

Amorim will come up against Mikel Arteta, who took on the ­Arsenal job almost five years ago when the club were 10th, giving parallels to United’s predicament, and has turned them into title contenders. “Sometimes coaches are just judged about the titles, but what he has been doing in Arsenal is amazing,” Amorim said.

“It transformed the team. He bought some youngsters that now are the big talents in this country. I hope to have the same mindset that he had in the difficult moments because I followed the Premier League for a long time.”