Quick-Step Floors riders Laurens De Plus and Petr Vakoc were left hospitalised following a collision with a truck in training.
De Plus and Vakoc were on a practice ride with team-mate Bob Jungels, who was not injured, in South Africa when they were hit from behind.
A Quick-Step statement said Vakoc was left with several fractured vertebrae and will undergo surgery later on Friday, while Laurens escaped with several abrasions and a minor pulmonary kidney contusion and should be released from hospital in a few days.
Speaking about the incident, Jungels told the team's official website: "The three of us were out training, when suddenly I heard a loud noise and then in the following second I saw Laurens and Petr on the ground.
"I did not see the truck coming from behind, but it must have hit them with the left front mirror or even the front left part. I ran to them and could see they were injured, so I did not dare to move them.
"A lady who was on the side of the road came and helped us, calling the ambulance, while our trainer Koen and I talked with them.
"It was really tough to see them like that and I hope they will get over this difficult moment soon. I wish them a fast recovery."