Berti first fell ill before last Tuesday's performance (Oct. 16), for which he was replaced by Roberto Alagna, who gained some notoriety in the part last year. (Alagna's performance at the Met was widely considered a success.)
For last Saturday's matinee (Oct. 20), Franco Farina had been announced as Berti's substitute. But Farina himself had fallen ill by that morning, and cover Stephen O'Mara went on with just a few hours' notice, making his Met debut in a solo role. (He had previously sung chorus roles in the house.) O'Mara will sing in Berti's place again this evening; the Radames for the remaining performances (October 27 and 30 and November 2, 5 and 8 is to be announced.