Brady made his Ireland debut in a friendly victory over Oman last month and boss Giovanni Trapattoni drafted in the 20-year-old for the crucial qualifiers against Germany and the Faroe Islands once he learned the full extent of Doyle's injury.
Wolves striker Doyle suffered thigh muscle damage in training earlier this week.
A statement released by the Football Association of Ireland said: "The Football Association of Ireland today announced that the results of Kevin Doyle's scan showed clear signs of a muscle injury that will rule the player out of international duty for the forthcoming double-header.
"Robbie Brady, who was on standby will be called up in his place."
Source: AFP
Source: AFP