Luidam, the horse that jumped a superb double clear for Billy Twomey to clinch Ireland's victory in last week's Aga Khan Cup in Dublin, will not travel to Athens.
The stallion has had ongoing problems with a sand crack in his near fore and, as a result, was named only as reserve for Athens.
But according to chef d'équipe Ned Campion, the horse was "only about 60-per-cent sound" after Dublin and was withdrawn yesterday.
"It wouldn't be fair to the horse to take a chance with him and it wouldn't be fair to the other riders to take him as a substitute if he is lame. It's very disappointing for Billy, but that's sport," said Campion.
Captain Shane Carey, winner of the Power Speed class at Dublin, has been named as the replacement. The Army combination were competing in Mill Street, Cork, when Carey was informed of the change.
The showjumpers fly out of Munster, Germany, on Monday.