Team Ireland High Performance Show Jumping Director Rodrigo Pessoa has stepped away from his role after airing his intention to compete for his native Brazil at next summer's Tokyo Games.
Ireland's show-jumping team qualified for the Olympics last month under Pessoa's guidance, becoming the first Irish show-jumping team to make a Games since Athens in 2004.
For the first time in history, Ireland will be represented at an Olympic Games by teams in eventing, dressage and show jumping.
However Pessoa, 47, will not lead the charge in Japan as he instead intends to seek selection for the Brazil team as a rider.
"Representing your country at the Olympics is one of the highest honours in sport and we wish Rodrigo the very best on this journey," said HSI chairman Joe Reynolds.
"From an Irish perspective, his decision to seek a position on the Brazilian team, which will compete against Team Ireland in Tokyo, makes it impossible for him to continue as senior high performance show jumping director at Team Ireland.
"Everyone at HSI wishes him all the best on a personal level as he seeks to represent his country again next year."
Pessoa, who took on the role in March 2017, added: "I have enjoyed my tenure as Ireland team manager. I am proud to have helped them to attain Olympic qualification and will always be available as a support to the team in the future.
"I would like to thank the entire High Performance Committee and all the team at Horse Sport Ireland. Last but not least I have to thank all the riders and owners for their participation."