The great Manchester United manager has announced his retirement as manager, with his 26-year reign at Old Trafford to finish at the end of the season, and his exploits will never be repeated according to Allardyce.
"What an outstanding job he's done. It's unlikely we'll see anybody of the likes of Alex Ferguson as a football manager lasting so long ever again.
"He took on the mantle where Sir Matt Busby left off and probably achieved even more than that.
"It is just an outstanding achievement for him and everybody at Manchester United, and of course his family."