Poul's horse, Tabasco Tari, had a slight injury that he appeared to have fully recovered from. But during preparations for the Games, the injury recurred.
"I'm not going to Kentucky for the medals. It is a fantastic opportunity at the highest level," van Grunsven said.
She is still a dressage team reserve with IPS Painted Black, who was recently sold to young Spanish rider Morgan Barbançon. She still trains the stallion and while in Kentucky will also work with eventer Tim Lips.
The Dutch dressage and reining horses left Liege, Belgium, and arrived in Cincinnati, Ohio, on Thursday. They were accompanied by flying team vet Jan Greve, and all travelled well, according to reports.
The Dutch reining team now consists of: Fenna Elzinga (Lelystad), Anky van Grunsven (Erp), Hubertus Heule (Aubrey, Texas) and Rieky Young (Vorstenbosch).
Hubertus Heule's horse, Crome Shiner, is travelling directly to Kentucky.