Van Garderen crashed twice in wet conditions on the 135km stage one between Chatou and Meudon, the first being a run-of-the-mill crash with other riders fighting for position, before a more serious crash after the American crashed into the back of a stationary team car while looking down to examine the damage to his bike.
"The initial crash wasn't so bad," van Garderen explained. "It was on a wide road when everyone was fighting for position and my tire was caught on a lip. The roads were wet and my wheel slipped out.
"I was able to get back up, and get going but I had trouble putting my chain back on and I noticed other damage with my gears and a puncture, so I thought I would have to change bikes.
"I was looking down to see what the damage was and next thing I knew I was on the ground as I had crashed into the back of a team car that had stopped on the road. I don't know if anyone was at fault as they had stopped for their rider."
Watch: Paris-Nice stage one highlights
Van Garderen was immediately taken to hospital following the second crash, where x-rays revealed a cervical sprain (a sprain in the upper spine), but no fractures or concussion.
BMC Racing doctor Dr Michel Cerfontaine said that the 29-year-old will be able to resume training in three to four days, before undergoing another x-ray next week to see how the injury is healing.
In a BMC press release on Sunday evening, van Garderen said that race medics had examined him for concussion after the crash, but that he had realised fairly quickly that he hadn't sustained any serious injuries and was disappointed to not be able to continue.
"I had the wind knocked out of me and I couldn't breathe. I also had pain in my upper back and neck so I couldn't really sit up," van Garderen explained.
"When the medics arrived and saw my helmet smashed and that I was having trouble breathing, they put me straight into the ambulance. After a few minutes, I realized it wasn't so bad.
"The medics went through some concussion protocols and I didn't show any signs of concussion. Fortunately, X-rays showed no fractures.
"It's good to take precautions but in the end, maybe I could have been able to continue. I have pain in my neck and a bit of a headache, but I don't feel nauseous. Above all, I'm really disappointed. I had good form at Volta ao Algarve and I was hoping to be able to capitalise on that."
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