Walker again showed great powers of recovery to get to the start line at the world championships, where she qualified second fastest in the time trial qualification but further injured the shoulder when she fell in practice on race day which put her out of the competition.
Walker had recovered fully and had trained well for the final World Cup until the spill in practice yesterday.
"You just wouldn't believe it. My bad luck just continues,'' Walker said.
She is hopeful of recovery in time for an international invitation event on the island of Curacao in the Caribbean in two weeks' time.
There are eight New Zealand men competing at Chula Vista, the Olympic BMX training centre, led by world championship silver medallist Marc Willers.
There is further practice today, qualifying time trials tomorrow and racing on Sunday (NZT).