Louis van Gaal has said he can understand if Manchester United’s supporters are feeling “scared” about the direction in which the club are heading, admitting that the deposed champions can almost certainly forget about winning the Premier League title back this season. “It is not a question of being champions at the end of the season because we have to build a team and that process takes maybe longer,” the new manager said, only one game into the job and with his squad’s deficiencies underlined again by a drastic shortage of players.

After losing his first game in charge at home to Swansea City last weekend, Van Gaal can at least bring in Robin van Persie for the trip to Sunderland on Sunday but that news is offset by what the manager claimed was the worst injury crisis he had experienced at this stage of the season since he started coaching almost 30 years ago.

In total there will be seven players missing now Ander Herrera has been added to the list by damaging his ankle in training while Marcos Rojo, the club’s new £16m signing from Sporting Lisbon, is ineligible to make his debut because of delays obtaining his work permit. Jonny Evans is still missing and that means Tyler Blackett is on standby again to play in the three-man defensive system that looked so vulnerable against Swansea.

Van Gaal has been disturbed by how quickly the new wave of optimism surrounding his appointment has faded. “Two weeks ago I was the king of Manchester and now I’m the devil of Manchester,” he said – and there was a flash of irritation when the subject turned to Danny Welbeck’s apparent availability.

Van Gaal is using a different room for his media interviews from Sir Alex Ferguson but there was a touch of the old manager about his snapped response. “I don’t speak to you about matters that are for the players. I don’t ask you if you are sacked tomorrow.”

The Dutchman went on to say that “the media were guessing” but noticeably stopped short of denying the stories, from well-placed sources, that Welbeck still wanted to leave Old Trafford, having initially told the club towards the end of last season. The England international, who would be of interest to Tottenham Hotspur, Everton and Arsenal, had been informed he could go if a suitable offer came in from a club outside the top six.

That has left the matter at an impasse and Van Gaal was unhappy that details of a private meeting had leaked. “I don’t speak about it. It’s private. I assume Danny Welbeck is not talking about our conversation. Ryan Giggs was also in that conversation. He won’t say anything either and that’s the way it should be.”

Welbeck was brought up in Manchester as a staunch United supporter and the idea that he could want to leave merely adds to the current upheaval at Old Trafford, with the club’s former player, Paul Scholes, saying earlier in the week they needed five experienced signings and that he has serious concerns they risked going into a longer state of decline.

“I can imagine that the fans are also scared,” Van Gaal said. “They have seen the last year and now they have seen the first home match. They have to believe in the philosophy that we are bringing to this club. The players are believing it. But it needs time, as I have already said. Paul Scholes has to believe in the philosophy.”

He added: “I’m not hired to be fired. I’m hired to build up a team. It’s a process and that process needs time. I am bringing another philosophy in the club and that’s difficult. It’s not an overnight job. You have to believe in it and maybe my CV can convince them. Otherwise, OK, I’m hired to be fired.”

Even with Rojo United have brought in fewer players than any other top-division club. A week ago Van Gaal said he was not concerned because “you can buy a player in 24 hours, believe me, that’s not a problem”. Now his message had changed. “The fans can think that [we need signings] but it’s not so easy to buy and sell on the football market. We respect every player [here]. I have tried to do that because I said everyone got a fair chance. We are doing it in the right sequence and it’s fair, polite and with a lot of respect to the players themselves.”