The 20-year-old Lyon-born midfielder feared the worse in July last year when a blister became infected and at one stage his condition was so grave, doctors thought they might have to amputate his foot.
Gonalons was fortunate enough to overcome the infection, although it did take eight months for him to regain his full fitness.
"I think the fact that I found myself not very far from death gave me a lot of mental strength," he told reporters after Tuesday's victory that put Lyon on the brink of qualification from Group E.
Normally employed as a defensive midfielder, Gonalons was asked by coach Claude Puel to stand in for centre back Cris after the Brazilian was stretchered off following a collision with Liverpool forward Dirk Kuyt.
"I was calm when I came on," Gonalons added. "I didn't let the emotion of playing at Anfield for the first time affect me."
Displaying maturity beyond his years from the moment he joined the fray, he capped a faultless performance by heading a 72nd minute equaliser.
"I saw the ball coming and I didn't ask myself any questions," he said of his first goal for Lyon. "After scoring I just didn't know where to go to celebrate. I'll remember this all my life."
Lyon had defensive problems before Cris got injured with Jean-Alain Boumsong, Mathieu Bodmer and Cleber Anderson all sidelined. As a result, Gonalons was paired in central defence with another midfielder, Jeremy Toulalan.
"I'm not used to playing in that position but with Jeremy, we talked a lot and did what he had to," Gonalons said.
Cesar Delgado sealed the surprise victory in stoppage time and Lyon now need just a home draw against Liverpool on November 4 to advance to the knockout stages.
"We need to congratulate Maxime Gonalons for that," Lyon goalkeeper Hugo Lloris told reporters. "He was magnificent."
