And Swiss brakeman Juerg Egger was flown to hospital with a back injury after a crash in training left his country's preparations in disarray.
Hefti, the world's top-ranked two-man pilot, suffered a head injury when he crashed at the 13th corner known as 50-50 during his first training.
He missed both practice runs on Thursday and failed to show up again on Friday, meaning he failed to complete the minimum of two training runs required to compete in the weekend's race.
"Beat suffered from bruises across his body and a concussion in the crash," said Christian Schlegel, the Swiss team's medical officer. "As a result he's not able to compete."
The 32-year-old won bronze in both the two-man and four-man events in Turin. He could still compete in the four-man event here as a crewman behind driver Ivo Rueegg.
Egger was injured when their third sled driven by Daniel Schmid rolled.
"He is okay, he has no severe injuries," Schlegel said. "He was brought to Vancouver by helicopter for further observation.
"He has a cervical spine injury. He can walk, he has no motor function disruption."
Switzerland were due to have three sleds in the two-man but are now down to one, driven by Rueegg who set the fastest time in Friday's opening two-man training run down the sun-kissed Whistler course.
Germany's Andre Lange, bidding to repeat the rare double he achieved in Turin when he drove to gold in the two and four-man, was quickest in Friday's sixth training run.
The two-man event begins with two runs on Saturday and concludes with two more on Sunday.