And second-favourite Jose Mourinho, the man who has been backed into 4/1 to be the next Manchester United manager, was once a 100/1 shot to replace Ferguson at Old Trafford.
Sky Bet first opened a market on Sir Alex's eventual replacement back in 2005 and customers who placed a bet on the then Chelsea boss in November 2005 could soon reap the rewards for their patience.
Moyes, who is currently at his shortest price of 2/5 following some significant backing on Saturday and renewed interest this morning, was out to 20/1 in November 2011.
Others once thought to be in the frame to follow in Fergie's footsteps include Martin O'Neill (2/1 in September 2005), Sven Goran Eriksson (9/1 in November 2005), Roy Keane (4/1 in April 2007), Carlos Queiroz (5/1 in April 2007) and Pep Guardiola (7/4 in December 2012).
Molde manager Ole Gunnar Solskjaer is currently 25/1 to be the next Manchester United manager, but was just 5/1 as recently as February, while former Leeds manager David O'Leary is currently the worst result in the book.
Jurgen Klopp is the 7/1 third-favourite after his good work at Borussia Dortmund has seen them win the Bundesliga and get to the forthcoming Champions League Final at Wembley in the last few years.
Ryan Giggs is 33/1.
Sky Bet's Head of Trading Sandro Di Michele said: "It depends how much money the board have but I'm not sure they want to spend £13 million to get the Special One out of his Real Madrid contract. Jose doesn't generally build teams for the future however he will guarantee instant success.
"A more long term and cheaper appointment would be David Moyes, while there is talk of Solksjaer returning to Old Trafford, but it would be a big gamble to take someone with such little managerial experience and no experience in England, let alone at a club the size of United."