Louis van Gaal has pointed the finger at Manchester United's mounting injury list as the cause for their struggles this season.
The under-pressure Dutchman has seen his team fall 10 points behind Premier League leaders Leicester City and out of the top four after recording only two wins in their last 10 league games.
United have suffered an injury crisis during that period with eight first-team players - Luke Shaw, Matteo Darmian, Ashley Young, Marcos Rojo, Phil Jones, Michael Carrick, Antonio Valencia and Bastian Schweinsteiger all missing games.
Van Gaal's relationship with frustrated United fans has grown increasingly strained in recent weeks.
He was booed off the pitch at Old Trafford after last week's loss to Southampton but he insists the team's injury woe is making his job difficult.
Speaking ahead of Friday night's FA Cup clash at Derby County, Van Gaal said: "When you see the circumstances that we have eight injuries, you cannot say that is the manager's fault because there are five or six contact injuries and also in the same positions.
"We have been first in the Premier League, may you remember that. That was one and a half months ago but the injuries are now and that is also a problem.
"When I can prevent that then OK, maybe I am guilty, and then I have to step down. But I don't have that feeling."
Van Gaal's defiance comes despite the fact United's current points total of 37 points from 23 games is their lowest ever in the Premier League, worse than the mark of 40 set by David Moyes in the tumultuous season which cost him his job.
The 64-year-old has signed 18 players over three transfer windows for a cost in excess of £250m, while allowing 35 players to leave the club.
Players such as Angel Di Maria, Javier Hernandez, Rafael, Jonny Evans and Nani could have been assets this season if they were kept by Van Gaal but he insists he cannot be expected to have foreseen the injury crisis which would grip his squad.
Van Gaal said: "You can say it was better to have kept all the players in the summer but I have explained already that we are convinced of the fact that you have to motivate the players and when you have big selection that is more difficult. At that time I could not predict we would have eight injuries."
United are in danger of missing out on Champions League qualification for the second time in three seasons as they currently sit five points behind fourth-placed Tottenham following their poor run of form.
Van Gaal still believes it is possible to salvage United's season and achieve the club's minimum target but he says his players must rediscover their self-belief if that is to happen.
"It is dependable when the players are coming back. We have five injuries that are normally long-term injuries because they are contact injuries," Van Gaal said.
"But we can fulfil the expectations. I am more dependable on belief than facts. The fact is now that we are not in the top four, the gap is bigger, so the belief is not so easy to believe."
Despite United's poor form, Van Gaal remains adamant he is the right man for the job and has no intention of walking away.
"Everybody knows I have signed a three-year contract and I have said it is a process. It is not one game it is a process and I want to continue until the end," Van Gaal said.
"If I was not willing to do that, I don't think I would have started here one and a half years ago.
"When I say things to defend myself then it is not good. Why do I have to defend myself? It is not good when I am always here in the press conference to defend myself. I don't want to defend myself, I want to analyse what is happening at Manchester United."