Huesca started their maiden LaLiga campaign with a 2-1 win at fellow minnows Eibar before claiming a 2-2 draw at Athletic Bilbao.
But an 8-2 thrashing at the hands of champions Barcelona led to a collapse in their from, Huesca winning a single point since.
With the club two points adrift of safety going into the international break, Huesca confirmed Franco's sacking on Tuesday.
"Huesca appreciates the commitment and great dedication shown during all his positions at the club and having been part of a project that he has helped grow," a club statement said.
Former Argentina goalkeeper Franco, who ended his playing career at the club, was appointed as Huesca's head coach in June, replacing Rubi having previously been director of external relations.