Hoy is competing competitively for the first time since the Beijing Olympics
Sir Chris Hoy crashed out of the men's keirin final on day two of the World Cup meeting in Copenhagen and will not compete on the final day.
The 32-year-old was vying for a second gold medal but brushed against Kevin Sireau, fell out of the race and was later taken to hospital for checks.
Sireau went on to claim victory, with Britain's Ross Edgar fourth.
The team pursuit quartet were the only Britons to top the podium on day two after three golds were won on day one.
Hoy, competing competitively for the first time since the 2008 Beijing Olympics, was expected to add to the tally in the men's keirin - one of the events in which he triumphed at the Laoshan Velodrome.
Hoy suffered scabbing and bruising on his shoulder and side
The Edinburgh rider won his opening round before leading fellow Scotsman Edgar into the final with victory in the second round.
But Hoy, who only returned to serious training last month when the British squad spent four weeks in Australia, tumbled out of the final while taking on France's Sireau.
He will now miss out on Sunday's individual sprint after suffering scabbing and bruising on his shoulder and side. He has also suffered a bruised hip, but an X-ray showed no fracture.
Victoria Pendleton, who won sprint gold in Beijing, was fifth in the women's 500m time-trial, 0.271 seconds behind winner Lisandra Guerra Rodriguez of Cuba, while Anna Blyth was ninth.
Blyth then combined with Helen Scott to finish fourth in the women's team sprint after losing out to China in their duel for the bronze medal.
David Daniell finished eighth in the men's one kilometre time-trial, while Alexandra Greenfield failed to finish in the women's points race.
Great Britain squad for Copenhagen World Cup:
Racing as SKY + HD team: Chris Hoy, Jamie Staff, Jason Kenny, Victoria Pendleton
Racing as Great Britain: Endurance - Rob Hayles, Chris Newton, Ed Clancy, Steven Burke, Pete Kennaugh, Lucy Martin, Alex Greenfield; Sprint - Ross Edgar, Matt Crampton, David Daniell, Anna Blyth, Helen Scott
Racing as 100% ME team: Mark Christian, Andy Fenn, Luke Rowe, Erick Rowsell, Lizzie Armitstead, Katie Colclough, Joanna Rowsell
Friday: women's sprint, men's team sprint, men's individual pursuit, men's points race, women's scratch race, women's individual pursuit
Saturday: men's team pursuit, men's keirin, women's team sprint, men's scratch race, women's points race, women's 500m time trial, men's 1km time trial
Sunday: men's sprint, women's team pursuit, women's keirin, men's madison