Spackman, who has left with the club enjoying a healthy fifth place in the First Division and looking forward to Saturday's FA Cup quarter-final against Coventry on Saturday, will remain with the club as a player until the end of the season, despite McDonald's outburst.
The chairman hopes to appoint a successor quickly, with the available Lou Macari thought favourite, although the name of Scarborough's Mick Wadsworth, who turned down an offer to become Spackman's assistant last week, is also thought to be in the frame. An announcement is likely to be made today. The coaches Steve Thompson and Russell Slade took charge for last night's game against Ipswich.
Spackman is thought to have grown frustrated with the board's policy of putting balance sheets before team sheets and shedding some of the club's best players, of whom he had been forced to sell five in the last four months.
The 37-year-old, who had worked without a contract and when questioned on the subject always said he was in negotiations, clearly decided he had had enough - especially following the recent departure of his coach, Willie Donachie, to join Joe Royle at Manchester City.
McDonald accused Spackman of putting himself before the club and believes the former Liverpool, Chelsea and Rangers midfielder was not up to the task of running a team on his own.
"Spackman was never the same man after Willie Donachie left," McDonald said. "When the pressure came he couldn't cope with it. I was persuaded to give him his chance when we lost Howard Kendall to Everton. I had an experienced manager up my sleeve then - and I do now. But Nigel got the job, although I was never 100 per cent sold on him. And today it looks as if I have been proved right.
"By going now he has put his own self-interest ahead of the club. And no one can forgive that. We spoke [on Monday] night and I asked him about his problems. It turned out to be all hot air. At the end of the day he was not experienced enough to handle it."
Spackman's decision appears not to have been an impulsive one, even though he was interviewed by The Independent's Guy Hodgson on Monday and gave no indication that he was about to leave.
"I made my decision to step down over the weekend," Spackman said yesterday. "My decision was not an easy one, but I have taken it and it stands. In my letter to the chairman I said that if it was the board's wish I would stay in charge of the team against Ipswich and against Coventry on Saturday, but in the absence of any response to that letter today, I have to assume that this offer is not acceptable."
McDonald was unapologetic yesterday for being careless enough to lose a manager who has produced such an upturn in the club's fortunes.
"I came in here with a plan - to prevent relegation, to stabilise the club, to build a new stand and to float the club on the stock market," he said. "All I ask is that people look at the mess I inherited and if that isn't progress I don't know what is."Reuse content