The French 14th seed prevailed after four hours and 43 minutes of energy-sapping tennis, which included an Australian Open record 71-shot rally.
Simon had to be taken to hospital following the match, and revealed that he was struggling to keep a grip on reality as the match entered the final stages.
"I was in bad shape," said Simon. "I felt I played the end of the match like in a dream, like I was not even on the court.
"I was just hitting the ball, trying to run, trying to catch it, and not thinking any more.
"I was too tired to be happy or upset or thinking or - I think at the end of the match I just completely lost control."
The 28-year-old will play Andy Murray in the last match on Hisense tomorrow.