Alex Ferguson threatened to quit Manchester United the year before leading the club to an unprecedented treble.
Former United chairman Martin Edwards revealed Ferguson was close to walking away after finishing second behind Arsenal in the 1997-98 Premier League season.
Edwards, who was chief executive at the time, says talks with then-chairman Roland Smith led to the Scot saying he would quit United, but he later changed his mind and the club went on to win the Premier League, FA Cup and Champions League in the following campaign.
"We hadn't won anything and to be honest we were dissatisfied," Edwards told the Daily Mail. "We wondered if Alex had taken his eye off the ball a little and if his celebrity status and interest in horses had maybe not helped.
"So we told him our feelings and Roland thought we should follow it up with a letter. He received it and came pretty much straight back in to see me. He was furious, saying: 'If that's what you think of me then get stuffed... I am resigning'. And off he went.
"I can't say I was particularly concerned as I thought he would come back. Happily, I was right. He had obviously had a word with somebody. It could have been his solicitor who would have told him that if he resigned he wouldn't be entitled to any money. But I don't know, I am speculating.
"But there is no point in worrying. If you feel it's the right thing to do - and I know it was - then you have to take the consequences. He was going to respond one way or the other and I would have been hugely unpopular had he walked.
"But the next year we won the treble so thank goodness he didn't go! Alex was brilliant and hugely successful. There weren't many blips."
Edwards, who is promoting his new book Red Glory: Manchester United and Me, also confirmed Ferguson was close to being sacked by United in the 1989-90 season, at the end of which the club won the FA Cup, his first trophy at Old Trafford.
"I was getting a huge amount of mail from supporters at that point, every single day," Edwards said. "All saying to get rid. I really wanted it to be successful so we were just hoping.
"We knew how hard Alex was working with the youth [team] and everything but had we gone to the end of that season without improvement we may have had to do something.
"It was another crucial moment in time but you don't think like that. You just think: 'Come on Alex, turn it round'."
In total, Ferguson won 28 major trophies at United, including 13 league titles, five FA Cups and two Champions Leagues before standing down in 2013.