Backed as a potential champion at Melbourne Park by no less than John McEnroe this week, the Canadian sixth seed looked like slumping out of the year's first Grand Slam after an error-prone first two sets on Margaret Court Arena.
The 22-year-old appeared to get fired up by a complaint to the umpire about the state of the balls early in the third set, however, and suddenly was a different player, serving like a dream and imposing his game on the world number 53.
"It's quite simple, you have to put the ball in the court without missing," Auger-Aliassime laughed, explaining the transformation.
"At the end of the day, it's not rocket science. So I was just trying to put one more ball in the court and make it simple, make it work."
It was quite a contrast with the opening two sets when Auger-Aliassime overcooked his shots on both sides and sprayed 25 unforced errors, with Molcan gleefully taking advantage.
"The numbers show it but he was just way more consistent than I was in the first two sets," Auger-Aliassime conceded.
"I was just trying to find a way to stay a little bit longer on court, to make the match tough and make it last longer.
"When I was able to clinch that third set, I got a lot more of belief in myself, my thoughts were a lot more positive and then I was thinking: 'I've done it before maybe I can do it again, come back and win'.
"I'm really thrilled I was able to get it done. It was a tough day for me."
The Canadian, who lost the first set of his opening match against compatriot Vasek Pospisil on Monday, wrapped up the contest in just over three hours with a rasping forehand - the fifth time in his career he has come back to win a five-setter.