Mandanda missed the World Cup after cracking a vertebra in his neck in a collision with Guingamp's Mustapha Yatabare in a Ligue 1 match on May 17 but the 29-year-old claimed it could have been even worse.
The Marseille goalkeeper, who made his return to the pitch in a friendly against Willem II in July, claimed he could have become a tetraplegic - or quadriplegic - following the accident.
"In the heat of the moment you have no time to ask yourself questions," Mandanda told France Football.
"I wanted to get up but I sensed it wasn't possible and I went off on a stretcher.
"When I was on the stretcher the thought went through my mind: 'Will I recover in time to play at the World Cup?' I didn't realise how serious the accident was. I could have been tetraplegic and forced to give up football.
"The neurosurgeon admitted that to me the following morning having looked at the scans and the MRI. He told me I wouldn't be able to go to the World Cup but added I'd been lucky amidst the distress. It could have been much more serious."
Mandanda played 90 minutes on Saturday in his second match since the accident, helping Marseille to a 3-1 friendly win over Chievo Verona.
Ahead of his eighth season at the Stade Velodrome, Mandanda underlined how important it was to move on from the memory of his final match of last season, effectively pledging his future to Marseille after being linked with moves to Milan and Arsenal in the close-season.
"Leaving the club and the Stade Velodrome on a stretcher, injured, after all these years at the club would not have been great," he said.
"I want to have a good season with [Marseille] and erase last season as far as possible, as simple as that."
