FIFA rules allowed the 26-year-old Myrie, a former Philadelphia Union player, to be called up at least 24 hours before the team's opening match.
Mora, a 29-year-old full-back, injured his right Achilles tendon in training this week.
He became the fourth player in coach Jorge Luis Pinto's intended squad to drop out through injury.
- Sports & Recreation
- Costa Rica
- Heiner Mora
- Dave Myrie