At the Women's Olympic Gymnastic preliminaries, the current World Champion, Jordyn Wieber, came in 4th place out of 60 athletes. 24 athletes qualified for the all-around competition.
Jordyn wasn't one of them.
Why? Because of a "two-per country" rule that says only 2 athletes from one country can qualify for the all-around event. The rule was put in place to promote diversity and prevent a medal sweep.
Basically, Jordyn came in 4th place and didn't qualify, while the person who came in 28th place did.
The Women's Gymnastics leader-board:
The 4 gymnasts that technically qualified, but will not be able to compete are: