Star British cyclist Mark Cavendish is undergoing medical checks after a crash on stage one, forcing him to pull out of the Abu Dhabi Tour.
The Dimension Data rider, who won the opening stage of last year's race, hit the deck in the neutral zone shortly after setting off on Wednesday from Madinat Zayed.
The 32-year-old managed to get back on his bike, but was forced to abandon the event soon after.
Dimension Data confirmed on Twitter that he had fallen "on the same shoulder he broke last year" after a crash with Peter Sagan on stage four of the Tour de France.
"He got up and chased back to the peloton but had to abandon soon after. More info to come after medical check," Dimension Data added.
Later, Dimension Data doctor Adrian Rotunno said on the team's website: "Mark sustained a concussion and a whiplash injury after his crash today.
"Due to the concussion, we were not willing to risk rider safety and the call was made for Mark to stop the race.
"A serious neck injury has been excluded in hospital. He currently has some concussive symptoms and neck pain, but is otherwise stable. We will monitor Mark's condition closely going forward."
Wednesday's crash happened ahead of the official start of the 189km opening stage between Madinat Zaya and Adnoc School.
Television replays showed the incident appeared to have been caused when the race director's car slowed down in front of the peloton, which resulted in a groups of riders behind having to brake sharply, with several falling down.
