Willoughby, the senior world champion, had to fight through extra races to make the last 16 after finishing third in his heat.
"A couple of mistakes early kind of cost me, but I'm still pretty safe so I'll keep the energy for tomorrow,” the Australian medal hope said.
"It's a good little learning curve for me and I'll be better for it."
Riders will be split into two heats in the semi-final from about 11.30pm tonight (SA time). The top four from each heat after three runs progress through to the gold medal round at 1.10am (SA time).
Laura Hodges again watched on from the sidelines as the Opals lost their semi-final of the women’s basketball to the United States, 73-86.
