Belgian Kris Boeckmans is in an induced coma after suffering concussion and facial fractures in a crash at the Vuelta a Espana.
His Lotto-Soudal team said Boeckmans, 28, had suffered "severe facial trauma" and "will probably need surgery".
Five riders had to abandon after the accident, which happened on the eighth stage with around 50km left.
Jasper Stuyven of Belgium won the stage but he too later abandoned the race after breaking his wrist in the crash.
The Trek Factory Racing rider said: "After the finish my wrist was getting more and more painful. Unfortunately, the X-rays confirmed it is broken and that my Vuelta finishes."
Tejay van Garderen, one of Froome's main rivals, Ireland's Dan Martin and Nacer Bouhanni were the three other riders who pulled out.
A Lotto-Soudal statement said Boeckmans "has a concussion, three broken ribs and had a bleeding in his lung. The doctors will now keep him in an induced coma for a few days."
Britain's Chris Froome, who is trying to become the third man to win the Vuelta and Tour de France in the same year, avoided the crash and finished with the favourites as Esteban Chaves retained the race lead.
Colombian Chaves, who rides for Orica GreenEdge, was held up behind the crash but rejoined the main peloton and retained his 10-second lead over Tom Dumoulin of the Netherlands.
Martin's abandonment means Froome's Team Sky team-mate Nicolas Roche is up to third overall, 36 seconds back.
Froome remains one minute 22 seconds behind Chaves and 33 seconds adrift of Alejandro Valverde, the highest placed rider chasing the overall victory.
Stuyven won the sprint for the line at the end of the 182.5km race to Murcia with Spain's Pello Bilbao (Caja Rural) second and Frenchman Kevin Reza (FDJ) third.
Slovakian Peter Sagan, who had been among the favourites to win the stage, reacted angrily after his hopes were ended by a separate collision with one of the race organisers' motorbikes around 10km from the finish.
The Tinkoff-Saxo rider kicked his own bike and a motorbike, and then completed the stage more than five minutes behind the winner.
Stage eight result:
1. Jasper Stuyven (Bel/Trek) 4hrs 06mins 05secs
2. Pello Bilbao (Spa/Caja Rural) Same time
3. Kevin Reza (Fra/FDJ)
4. Giovanni Visconti (Ita/Movistar)
5. Kristian Sbaragli (Ita/Team MTN)
6. Tosh Van der Sande (Bel/Lotto)
7. Julien Simon (Fra/Cofidis)
8. Pieter Serry (Bel/Etixx - Quick-Step)
9. Jose Joaquin Rojas (Spa/Movistar)
10. Nicolas Roche (Ire/Team Sky)
26. Chris Froome (GB/Team Sky) Same time
General classification after stage eight:
1. Esteban Chaves (Col/Orica) 31hrs 12mins 18secs
2. Tom Dumoulin (Ned/Giant) +10secs
3. Nicolas Roche (Ire/Team Sky) +36secs
4. Alejandro Valverde (Spa/Movistar) +49secs
5. Joaquim Rodriguez (Spa/Katusha) +56secs
6. Nairo Quintana (Col/Movistar) +57secs
7. Fabio Aru (Ita/Astana) Same time
8. Daniel Moreno (Spa/Katusha) +1min 18secs
9. Domenico Pozzovivo (Ita/AG2R) +1min 19secs
10. Mikel Nieve (Spa/Team Sky) +1min 21secs
11. Chris Froome (GB/Team Sky) +1min 22secs