Sam Allardyce has described the transfer window as being "out of control" and fears he could lose his job if he signs the wrong players this month.
The West Ham United manager has had a busy January so far, recruiting Joe Cole from Liverpool, Marouane Chamakh on loan from Arsenal and Wellington Paulista from Cruzeiro.
But despite that early success, he regards the winter window as a nightmare part of the season that can end up doing more harm than good.
He said: "If I make mistakes in the transfer window and bring in players that fail, it costs me my job. It gets me the sack.
"The window has always been out of control since it started 10 years ago. It has never been in control.
"It has never been an ideal situation in any way, shape or form during the season.
"It's obviously a very disruptive time of the year, the back end of December and the beginning of January.
"I try very hard not to let the window use up all my time. I pass it all on to Martin [Glover, head of recruitment] and he is panicking a bit at the moment because he can't get any sleep at all."
Allardyce revealed he receives "thousands" of offers during the January transfer window, but insisted any moves have to be carefully considered.
He said: "I will be able to tell you exactly how many players West Ham have been offered when the window closes at the end of the month because I keep a note of everything. Right now I can tell you that it will run into the thousands.
"It is not luck - you cannot rely on luck. You have got to rely on the information you can gather and try to make a calculated choice that this is the right one for you.
"All clubs miss out because sometimes they do not know certain players are available to buy or they did not want to come.
"Then, as it goes on, people do become available and sometimes you take a player and then you get a player come back to you that you have been negotiating with and you kick yourself and think, 'If I had just waited a few days longer'."
Allardyce also revealed he missed out on the chance to sign Samuel Eto'o during his time as Bolton Wanderers manager.
The Cameroon international went on to become one of the most celebrated strikers in world football, winning two Champions League titles with Barcelona and a third with Inter Milan.
Allardyce explained: "We could have got Eto'o for £6.5million from Mallorca but the chairman was too tight to pay at the time, even though I said there was a £20million player on a plate for him."