According to a press release from the Met, “René Pape has withdrawn from the Met’s 125th Anniversary Gala on Sunday, March 15, due to illness.”
 
The cancellation starts a daisy chain of cast reshuffling, so listen carefully: John Tomlinson will sing the Death Scene from Mussorgsky’s Boris Godunov, replacing Pape.  James Morris will sing Wotan in the final scene of Wagner’s Das Rheingold, replacing Pape. And John Relyea will sing “Le veau d’or” from Gounod’s Faust, replacing Morris.