Britain's Chris Rawlinson crashed out of the men's 400m hurdles after a disastrous run in his semi-final. The 32-year-old came to Athens confident of a medal, but clattered the first hurdle and trailed home in 50.89 seconds to finish last.
Hot favourite Felix Sanchez looked relaxed as he moved effortlessly into the final in 47.93 seconds.
But defending Olympic champion Angelo Taylor could finish only fourth in his semi and will not retain his title.
Rawlinson was carried away from the track on a stretcher with an ice pack on his knee, and must now be considered a real doubt for the 4x400m relay.
A statement from UK Athletics said that Rawlinson had injured the lower quadricep in his left knee.
He will be distraught at failing to make the final, having disappointed in the big championship races all too often.
He has been in great form all season and had raced sparingly, even talking up his chances of beating Sanchez.
Sanchez, the world champion, remains undefeated over the distance for the last three years.
And he is desperate to make amends for the Sydney Olympics where he crashed out in the semi-finals.
"I was thinking about Sydney as I warmed up and I was dejected and sad," said Sanchez.
"The Olympics have been a long time coming and I'm really motivated to get to the final and hopefully I'll get a medal."
MMIX
E-mail this to a friend 
Printable version 
The defining images