José Mourinho has admitted Manchester United’s preparation for the new season is “very bad” because many of his senior players are resting after the World Cup and Alexis Sánchez may miss the club’s entire US tour because of a visa matter.

United are in California but Mourinho is without Sánchez, Paul Pogba, Romelu Lukaku, Marouane Fellaini, Marcus Rashford, Jesse Lingard, Marcos Rojo, Victor Lindelöf, Ashley Young, David de Gea, Nemanja Matic, Fred and Phil Jones.

De Gea, Matic and Fred are due to join the squad next week before the third tour game against Milan in Los Angeles. Yet Mourinho said: “The pre-season is very bad. The positive thing is only for the young boys that have a fantastic opportunity to train with us.Next week will come De Gea, Matic and Fred which is good, especially for Fred.

“He is a new player with us but everything is really bad and then we go to the UK and have to play the Premier League. The broadcasters were not nice to us with the Friday match [against Leicester City on 10 August], which complicates more things.

“So I’m worried because I’m not training [with everyone] and then I go to the Premier League without lots of players. But it is what it is and we have to try and make the best out of it with the players we have here.”

Mourinho is also without Diogo Dalot, the 19-year-old full-back signed from Porto for £19m, because of injury. The loss of Sánchez is a particular blow because Mourinho aims to field a frontline of the Chilean, Juan Mata and Anthony Martial against Leicester .

“It is really bad, really sad, not good for him, for me, the team,” the manager said. “There is no one to blame; the club is making the effort. I have to respect the US authorities in their process of visas. But hopefully he joins us later because it could be important to work with Martial, Alexis and Mata – the players we have in attack for start of the season. There is no Lukaku, Lingard or Rashford.”

Mourinho was noncommittal regarding any further signings. “I’ve no idea. I’m not going to lie to you, I’m not going to say somebody is coming or nobody is coming.”

Pogba was a driving force in France’s World Cup triumph. Mourinho hopes the midfielder can finally replicate that form over a whole season.

“I hope he understands why he was very good. That’s the point about his performance level and contribution to a winning team: it is to understand why he was so good especially in the second part of the competition, where he was absolutely brilliant.”

Luke Shaw has vowed to prove to Mourinho he should be the first-choice left-back. “Of course, I’ll look at it like that,” he said. “The next five games [of the tour] are all about fitness, but I want to try and prove to the manager that I can be in his team, not just in these games.

“When everyone comes back and everyone is fit and ready, I still want to be that first name on the teamsheet. It’s time for me to show him over the next four weeks what I can do and why I deserve to be in this team.”