Liam Phillips was aiming to advance to the BMX semi-finals on men's quarter-final day at the London 2012 Olympic Velopark.
The 23-year-old from Burnham-on-Sea bounced back from a broken collarbone sustained at May's BMX World Championships in Birmingham, a day after winning time-trial silver, to qualify in 12th position.
Three-time world champion Shanaze Reade qualified fifth in the women's event, which resumes with Friday's semi-finals. Phillips was aiming to join Reade in competing for a place in the final.
The Somerset rider was drawn in the second quarter-final heat, with five runs to determine whether he will advance, and was satisfied with his ride.
"It's a good start," he said. "I'm in good shape. The race to the first turn, that's the most important part and that part of my lap's better than it ever has been, even at the world champs.
"It's pretty scary to come off the back of an injury and be going faster than you were at the world champs 10 weeks' ago.
"That's certainly the case in my book, but in BMX anything can happen, it'll be a lottery.
"Whatever happens in terms of results, I'm here to enjoy it and to have 6,000 people that have paid to come and watch a sport that I've done since I was five years old is mind-blowing."
Reade qualified in fifth in the corresponding women's event as world time-trial champion Caroline Buchanan of Australia advanced in first place.
Reade and Buchanan were set to meet in the same semi-final heat, featuring three runs, on Friday.