The world number two, defending his only remaining Grand Slam crown, was pegged back from two sets up before scoring his first-ever win over Simon, 6-2, 6-3, 4-6, 4-6, 6-3, to stay on course for his fifth Open title.
It was a desperately close call for the 29-year-old, who holds a record 16 Grand Slam titles and only narrowly avoided his worst performance at a major in eight years, and his poorest ever Australian Open outing.
