Olympic champion Evenepoel retains world title in 'toughest time trial'
Olympic champion in Paris, Evenepoel matched Ganna on the flat and gained on him in the rolling sections before Ganna, a double world champion himself, went for broke in the home straight to set up a razor's edge finish.
Instead of shooting down the ramp, the distracted favourite Evenepoel took time to gather his nerve for a slower than expected start.
On his gold Olympic champion's bike, Evenepoel showed deep reserves of nerve and stamina to cling onto the lead over the final section of the 46.1km run along Lake Zurich.
"I felt good at the start physically, then struggled on the hill without quite going too close to the limit," said the plucky Quick Step man.
"But this is the world championships and you have to give everything, it was easily the toughest time trial of my life."
Evenepoel won the time trial and the road race at the Summer Games and next Sunday can repeat that here in Zurich on the world stage.
"Tadej Pogacar is favourite but I came here for the title and I'll be trying for that," said the Belgian.
Should he win next Sunday it would be a 60th top level win at the age of 24, despite a long lay-off due to falling over a stone wall into a ravine at the Tour of Lombardy four years ago.
After Evenepoel had described the road surfaces of Paris in the harshest terms at the Olympics, the pristine surfaces of Zurich would have been more suited to the larger, more powerful Ganna, but he finished 6sec behind the winner.
An unheralded rider until this season but European time-trial champion just a few weeks ago, Affini was again celebrating after he flew under the radar as incidents befell others to deprive them of a shot at the podium.
Australia's Jay Vine finished covered in blood when a fall ended his hopes of bronze, but he showed great courage by clambering back into the saddle with blood running from a cut at the top of his nose.
Other disappointments concerned Briton Josh Tarling, who came fourth, Slovenian Primoz Roglic who wilted badly and local hero Steffan Kung who hung his head at the finish line.
Of the lesser lights who also star at the world championships, Uganda's Charles Kagimu was first down the ramp while Ahmad Badreddin Wais of the Refugee Cycling Team scampered down it with sheer delight as second rider on the course.
