On Tuesday, Dutch Olympic dressage rider Adelinde Cornelissen entered the arena on her horse Parzival, guided him through a few movements, then stopped, raised her hand in salute and rode off the field and out of the competition.
The heartbreaking decision was the culmination of a huge amount of soul-searching but in the end Cornelissen decided to put the welfare of her horse ahead of her own Olympic ambitions and those of her teammates.
Days earlier, Parzival had been bitten on the face by a poisonous insect and developed a fever. Cornelissen stayed by his side all that time, even sleeping in his stable with him.
She asked equestrian governing body the FEI if she could change places in the competition starting order to give him more time to recover but the request was denied.
Ahead of his scheduled performance, however, Parzival was given a clean bill of health, and knowing that her teammates were relying on her, Cornelissen decided to compete.
"The temperature was back to normal, he looked fit, was eating and drinking good," she wrote in a Facebook post. "I also didn't want to let the team down... In the back of my mind knowing we had no reserve combination here... Nobody to fill in my place if I would withdraw, letting the team down.
"The FEI vets came and checked up on him around 10am. All gave green light to compete. We decided I would give it a try.
After starting her routine, however, Cornelissen sensed something was not quite right with Parzival and decided she just didn't want to risk injuring the horse she had thought of as a friend for 19 years.
"When I entered I already felt he was giving his utmost and being the fighter he is, he never gives up...
"In order to protect him, I gave up... My buddy, my friend, the horse that has given everything for me his whole life does not deserve this... So I saluted and left the arena..."