Injured Brazil goalkeeper out of Olympics
A scan showed the Santos keeper's elbow was badly bruised during practice on Monday and he would not recover in time to take part in the men's soccer tournament at the London Games, team doctor Jose Luis Runco said.
Fiorentina's goalkeeper Neto will replace Cabral in the first team, while 19-year-old Gabrial, from AC Milan, will be the substitute.
Coach Mano Menezes will call up a replacement, the CBF said on their official website.
Favourites Brazil kick off against Egypt in Group C on Thursday.