The 67-year-old Scot, who has guided the Red Devils to 11 league, five FA Cup and three League Cup titles, as well as the Champions League in 1999, had originally announced that he was ready to walk away from Old Trafford at the end of the 2001/02 campaign.
However, he eventually changed his mind, and will oversee United finally usurping Liverpool's joint-record of 18 league crowns should they claim a fourth consecutive Premier League gong this term.
And Bayern boss Van Gaal, who was in charge of the Dutch national team for the 2002 World Cup before returning to Barcelona for a second spell, has revealed that he would have been heading to Manchester instead had Sir Alex retired.
"It was before the World Cup of 2002," he said.
"I was in contact with Manchester United through Peter Kenyon.
"It was said to me that Alex Ferguson was going to retire.
"The moment he'd go, I'd succeed him. But in the end Ferguson didn't want to quit."
