Louis van Gaal has confirmed he is down to just one fit centre-back for Manchester United's home game against West Ham on Saturday.

Marcos Rojo is the only senior central defender available for Saturday's match, the United manager revealed at his pre-match press conference on Thursday.

Evans suffered a bruised ankle injury in the 5-3 defeat to Leicester and Tyler Blackett is suspended following his dismissal at the King Power stadium.

Chris Smalling was injured in training on Wednesday and will not feature against the Hammers while Phil Jones remains sidelined with a hamstring problem, the United boss said.

"Smalling yesterday ran out of the training session because he had stiff legs. We have to see what that means."

Van Gaal said: "All the three right-sided centre-halves are out.

"I don't know how long they will be out for.

"Evans is a very difficult one. His bone is bruised a lot and we have to wait and see, to evaluate it.

"Smalling yesterday ran out of the training session because he had stiff legs.

"We have to see what that means. But I don't take risks with players."

The injuries to Smalling and Evans have come at a terrible time for Van Gaal, who watched his weak defence crumble to a shock defeat at Leicester last weekend.

The Dutchman, who has won just one of his opening six matches, will have to look for alternatives for the visit of West Ham, who beat Liverpool last weekend.

Midfielders Daley Blind or Darren Fletcher could be used as emergency centre-backs.

Van Gaal is also considering handing 19-year-old Paddy McNair his debut, but denied he would be taking a risk if he drafted any youth players into his starting XI.

"They are always ready, I think," the former Ajax boss said. "They have hunger to play the game and Manchester United youth education has a certain level that can provide that.

"It's a big difference (between youth football and the Barclays Premier League), but in one game you can show yourself."

This is a big challenge. This club is in a transition. At the start (on tour) we won all of our games in very difficult circumstances. Now we are in difficult circumstances and you can win."

Van Gaal is without another six injured players, including senior personnel like Michael Carrick, Marouane Fellaini and Ashley Young.

"I have to admit that I have never been in this situation before (with injuries)," Van Gaal added.

"It is strange. For me it's difficult to understand. We are evaluating what we can do in a different way.

"But you have to train on a certain level because otherwise you can't play a game.

"I have already said I have adapted to a certain level but you cannot train lower because you then can't perform in the right way."

Despite United's poor start, Van Gaal is not panicking about failing to deliver the club's aim of a top-three finish.

The former Holland coach admits this could be the hardest assignment of his 23-year management career though.

"At this moment it is maybe yes (my toughest job)," said Van Gaal, who then repeated his call for calm among the United fans.

"But we have to see us in a year and not in a week where we have nine injuries and a red card. I don't think you can judge that effect.

"This is a big challenge. This club is in a transition. At the start (on tour) we won all of our games in very difficult circumstances. Now we are in difficult circumstances and you can win.

"We should have won last weekend - we had to win when we were 3-1 up."