Dutch cyclist Fabio Jakobsen was fighting for his life on Wednesday after he was thrown into and over a barrier at 80km/h in a sickening conclusion to the opening stage of the Tour of Poland.
Footage showed 23-year-old Jakobsen, of the Deceuninck-Quick Step, racing elbow-to-elbow with fellow Dutchman Dylan Groenewegen of Jumbo-Visma as both men frantically tussled in a tight sprint to the line in Katowice.
However, Jakobsen came off worst, somersaulting over the barriers before colliding with a photographer after Groenewegen had veered suddenly to the right, squeezing his rival into the security wall.
"His condition is very serious. His life is directly threatened," tour doctor Barbara Jerschina told Polsat Sport.
"Unfortunately, it is a serious head and brain injury. He has lost a lot of blood. He is very strong. I hope he will survive."
Governing body, the UCI said they strongly condemned the "dangerous behaviour" of Groenewegen.
Deceuninck-Quick Step tweeted: "Our thoughts and prayers are with Fabio Jakobsen. When we have news, we will let you know.
"Thank you from the bottom of our hearts for your support."
The incident comes a year to the day after the death of 22-year-old Belgian sprinter Bjorg Lambrecht, who died after falling and hitting a concrete structure on the 2019 Tour of Poland.
"It was an unfair fight and one of the riders suffered tremendously, two more suffered as well," Tour organiser Czeslaw Lang told TVP Sport.
Groenewegen went on to win the stage but was later disqualified with the stricken Jakobsen declared the winner.
The UCI said it "strongly condemns the dangerous behaviour of Dylan Groenewegen (Jumbo-Visma), who sent Fabio Jakobsen (Deceuninck-Quickstep) into the barriers a few metres from the finish, causing a collective crash at the end of the first stage of the Tour of Poland.
A statement added: "Groenewegen was disqualified from the race by the commissaires' panel.
"The UCI, which considers the behaviour unacceptable, immediately referred the matter to the disciplinary commission to request the imposition of sanctions commensurate with the seriousness of the facts."
Others who crashed in the ensuing pile-up included Marc Sarreau of Groupama-FDJ as competitors became entangled in a desperate bid to avoid each other as well as the debris from the destroyed barriers.
"Marc Sarreau suffers an important trauma to the shoulder and also from multiple tearing of the ligaments. He is going to need further medical tests," tweeted his team.
Damien Touze "remained conscious despite the fall. He is in hospital for further examinations," his Cofidis team tweeted.
The drama came at the end of the first stage, raced over 198km from Chorzow to Katowice in southern Poland.
Jakobsen is considered a rising star of the sprint in the peloton who made his name in 2019 with two stage wins on the Vuelta a Espana, one of the sport's three Grand Tours.
Having turned professional in 2018 with Patrick Lefevere's Quick-Step team, Jakobsen donned the Dutch champion's jersey in June last year.
In last year's Tour of Poland he was third on the opening stage.