Because it wouldn't be JJ without some added drama. It's being reported in the Serbian press that JJ has decided not to participate in tonight's opening ceremonies because of an injury she sustained during Friday morning's practice. Arm and shoulder injuries wouldn't keep you from marching. Leg and back injuries would. No word yet on what the injury is.
This is too bad. I was hoping to see her march and then, midway through, call for the trainer.
(Thanks to the posters at Tennis Forums for the sources.)
UPDATE: Apparently JJ did walk in the opening ceremonies. So she must have felt better.