Past speculation had claimed that Ferguson would have been removed from the position had Mark Robins not scored the only goal of the game during a tie against Nottingham Forest at the City Ground earlier that year.
Edwards has always denied that school of thought, but he has now conceded that things may have been different for the retiring Scot had his side not defeated the Eagles in a replay at Wembley.
"By 1990 we hadn't won anything and we'd bought a lot of players. But we knew how hard Alex was working, particularly at the youth level," Edwards told Sky Sports News. "We felt that given the time it would come right. It was just a question of whether the supporters would give us the time. Fortunately the success in 1990 [winning the FA Cup] revived everything. It saved us really."
Edwards went on to pay tribute to the 71-year-old, by adding: "He's a workaholic. He's got such a great knowledge of football and knows how to motivate people. I don't think you'll ever see anyone managing Man United for 27 years again."
Edwards was in charge of United when Ferguson was recruited from Aberdeen in 1986.