Earlier this week, Chris Froome crashed at high speed while warming up for the time trial at the Criterium du Dauphiné. Dan Martin, who was riding behind, says he feared the Team Ineos rider was dead in the immediate aftermath.
Froome had taken a hand off the bars to wipe his nose when a gust of wind took his front wheel, sending him into the wall of a house.
Sir Dave Brailsford said that Garmin data indicated he had gone from 54km/h to a "dead stop".
The rider suffered multiple fractures and underwent six hours of surgery on Wednesday night. He is now recovering in hospital.
Chief surgeon Remi Philippot told the BBC that Froome is facing "at least six months" away from cycling.
Dan Martin was riding a little way behind Froome when the crash took place.
"He blew his nose, the wind caught him and then he veered out in front of the team car,” he told Cycling News. “We didn't see what happened but we saw him hit the wall. He didn't have any chance to lose any speed. We didn't want to say anything yesterday out of respect for Chris and his family. It was up to Ineos to say what they needed.
"Refocusing after that was not an easy task. I was thinking about it last night and I'm still replaying it in my head. It's very, very unpleasant."
Recalling the immediate aftermath, Martin said: "Neil [Stephens, the UAE Team Emirates director] and I looked at each other in stunned silence and just stood there for 20 seconds, just shaking.
“I stayed by the team car and we asked if there was anything we could do, but I thought it could have been much worse. I thought he could have been dead. To see something like that isn't pleasant.”
He added: "That could have happened to anyone. It was a freak accident, with a freak gust of wind. It's happened to me in training but at a much slower speed. I once took my hand off the bars to take off an arm-warmer and the wind caught me and I was down. Chris is really unfortunate."